题目列表(包括答案和解析)
根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两处为多余选项。
Active ＆ Passive TransportRecall that all living things are made up of tiny units called cells, and that -cells are surrounded by a covering called a membrane (膜)．The membrane allows things to move in and out of the cell, and it also controls what can get through． 1 They must have water, oxygen, sugar, sodium, potassium (钾) , and a variety of other minerals．The body has to have a delivery system to get these materials where they need to go．In addition, every cell produces waste materials that it needs to get rid of． 2
Just like cars, trucks, and other vehicles form a transport system for the pick up and delivery of materials out in the world, the body has a transport system, too． 3
Passive transport is easiest for the cells because they don't need to use any energy to make it happen．Diffusion (扩散) is the simplest and most common form of passive transport．
During the diffusion process, tiny particles (微粒) of the materials that need to be delivered to the cells are spread through either a gas (like oxygen) or a liquid (like water)． 4 Osmosis (渗透作用) is a unique form of passive transport that allows water to pass through the cell membrane, but keeps most other materials out．
Active transport is used when the concentration of materials inside the cell is high, and the cell needs to push materials out to areas of low concentration of the materials．Unfortunately, this kind of transport requires the cell to work against the natural direction of diffusion, so the cell uses up energy． 5 They pump sodium out of their cells and pull potassium in．Although they must use energy in this process, doing so allows them to thrive (成长)．
A．Areas with high concentrations of the materials slowly diffuse them to areas of low concentration．
B．Cells need many kinds of materials in order to survive．
C．One example of this is the way that nerve cells work．
D．There are two kinds of transport：active transport, and passive transport．
E．Passive transport is much more essential than active transport．
F．The body has to have a method of waste collection and disposal．
G．Then the cell usually needs extra energy to make up for it．
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根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
Here are self-care steps recommended by experts．Make a promise to yourself to do the following．Choose where you want to start on your path．
Exercise, and at the very least, walk．
Exercise may be the most important step on a path to good health．Burning calories keeps your metabolism(新陈代谢)from slowing down and helps to prevent that last meal you ate from turning to unwanted fat． 1 The chemicals help you to feel happier and more relaxed than you were before you worked out．As long as you are able to manage a regular exercise rule of activity for 30 minutes a day, you’re in good shape．
2
The restorative powers of sleep are an amazing thing, and giving your body an adequate chance to recharge is one of the easiest things you can do for yourself to stay healthy．Sleeping gives your body the chance to heal and repair itself． 3 ．
Eat more vegetables, cut down on red meat, caffeine, sugar and salt．
You’ve heard this a million times before, but trading in red meat, caffeine, sugar and salt for vegetables is a keystone to good health． 4 And they are rich in essential vitamins and nutrients like potassium(钾)．
5
Eating breakfast is another easy step you can take on the road to good health．Studies have shown that people can lower their cholesterol just by eating a healthy breakfast．
A．Sleep regular hours．
B．Try drinking more water．
C．Never skip breakfast．
D．So give your body the rest it deserves．
E．Get up a little late and cook breakfast yourself．
F．Unlike sweet and salty foods, vegetables are low in harmful fats and calories．
G．It has also been shown to improve mood by stimulating various brain chemicals．
Although men and women have been growing crops for thousands of years, they have not always had enough to eat. Even today, many people in the world go hungry, and even die of hunger. If we are to grow enough for everybody, we have to grow more crops and better crops.
Plants need the right food in order to grow. In particular, they need three chemical substances (物质) in the soil: nitrogen (氮), phosphorus (磷) and potassium (钾). They also need smaller amounts of other chemical substances like calcium. If there is too little of any of these substances in the soil, plants can’t grow well.
When a plant grows, it takes up these basic substances from the soil and builds them into itself. If we remove the plant from the soil and use it for food, we are taking some of these substances away, and this means that future plants will find less of them in the soil. In time, the soil would become too poor for plants to grow in it at all.
To prevent this we must put basic substances back. One way of doing this is putting manure (肥料) on the soil. This contains the remains of plants that have been eaten, and, if we add it to the soil, we are returning some of the basic substances. In Europe and in Japan, manure from animals has for long been used in this way. Unfortunately much of the animal waste in India is used as fuel because there is not enough wood to burn. This means there is less manure for the crops.
Even when we use manure, we can not put back into the soil more of the basic substances than have been taken out. Often the soil does not have enough of them in the first place, and so we must provide extra supplies. We can use chemical fertilizers (化肥). Experiments in India have shown that, if we use a fertilizer containing a mixture of nitrogen and phosphorus, we get half as much rice again from the crops on any one piece of land.
46. According to the passage, how many methods are introduced to improve the soil?
A. One. B. Two. C. Three. D. Four.
47. The underlined word “this” (in Paragraph 4) refers to the fact that ____________.
A. the soil would become too poor for plants to grow in it at all
B. we are taking some substances away from the soil
C. the plant takes up these essential substances from the soil
D. even today many people in the world go hungry
49. To make sure that the soil has enough basic substances, people can _____________.
A. remove plants from the soil
B. provide the soil with extra supplies
C. plant as many plants as possible
D. stop planting in the soil
50. The passage is mainly about _____________.
A. why more food is needed
B. how to grow better crops
C. the fact that people have not always enough to eat
D. the essential substances that plants need
话题链接：Proper habits of nutrition can be developed by paying attention to the variety of foods included in the diet; and the quantity of each kind of food eaten．A diet, or the food regularly eaten, must contain all the nutritional(营养的)elements．Different food contains different vitamins(维生素)，let's look at the food one by one．
EGGS
Eggs are an excellent source of complete protein(蛋白质)；they contain all essential amino acids(氨基酸)．One large egg contains 7 or 8 grams of first-class protein．Also found in eggs are vitamins A, B2, D, and E; niacin(烟酸)；copper; iron; phosphorus(磷)；and unsaturated(不饱和的)fats．The egg yolk contains the richest known source of choline, found in lecithin and necessary for keeping the cholesterol (胆固醇)within the egg emulsified(蛋白)．The egg yolk also contains biotin(维生素H)，one of the B-complex vitamins．
FIBER
Fiber is the part of food that is not digested by the human body, such as the skin of an apple and the husk(壳，皮)of a wheat kernel．The normal functioning of the intestinal tract depends upon the presence of adequate fiber．A low-fiber diet has been associated with heart disease, cancer of the colon and rectum(直肠)，diverticulosis(瘢痕形成)，varicose veins(纹理)，phlebitis(静脉炎)，and obesity．
FISH
Fish are excellent sources of high-grade protein, polyunsaturated fatty acids, and minerals, especially iodine(碘)and potassium(钾)．Fish are categorized as freshwater fish, saltwater fish, and shellfish．These types differ slightly in nutritive value．Freshwater fish provide magnesium(镁)，phosphorus, iron, and copper．Saltwater fish and shellfish are rich in iodine, fluorine(氟)，and cobalt (钴)．Fatty fish, such as halibut(比目鱼)，mackerel(鲭鱼)，and salmon, are good sources of vitamins A and D．Herring, oysters, and sardines contain vanadium and zinc．Shellfish are low fatty acids but are relatively high in cholesterol．
FRUITS
Fresh fruits are good sources of vitamins and minerals, especially vitamin A and C, carbohydrates in the form of cellulose and natural sugars, and water．They are good substitutes of such high-carbohydrate(碳水化合物)foods as candy, cookies, and cakes, which contain few nutrients．Yellow fruits, such as apricots, cantaloupe(香瓜)，and persimmons(柿子)，are good sources of carotene(胡萝卜素)，which is converted to vitamin A．Aside from acerola cherries and rose hips, the best natural sources of vitamin C are the citrus fruits, such as oranges, grapefruit, lemons, and tangerines(橘)；other sources of vitamin C are cantaloupe, strawberries, and tomatoes．Apples and bananas contain valuable bulk fiber in the form of indigestible(不可吸收的)cellulose, which is needed for regular bowel movement．Bananas are high in magnesium(镁)and may be useful for treatment of diarrhea, colitis, ulcers, and certain cases of protein allergies．Bananas and pears are the highest in natural sugars．
GRAINS
Grains are often referred to as cereals ;they are the seeds of various grasses such as wheat, oats, rice, and barley．Often called the “staff of life”, they provide the bulk of the world's food supply．Common foods made from these grains are flours, breads, breakfast cereals, and macaroni．
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想一想：Healthy eating is the essential thing for the physical and mental development for human being．But the eating habit of our Chinese people is not very reasonable or suitable．If you are responsible for the improvement of the Chinese healthy eating, what will you do to change the formed eating habit of Chinese people?
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