3．Why are people interested in eating raw foods or whole foods？One reason is that eating these types of food reduces the risk of acid accumulation in your body．
Raw and whole foods are usually digested more efficiently than cooked and refined foods．When we cook foods，we destroy the natural enzymes（酶）that are part of the food in its raw form．These enzymes were intended by nature to help us digest the food．When we consume food without these natural enzymes，our bodies either digest the food improperly or allow too many nutrients to be absorbed into the bloodstream．In both instances，the result is obesity．When too many nutrients are absorbed at once，the body grows fat．Improperly digested food moves slowly through the digestive tract，where it becomes increasingly acidic （酸性的）．To protect its vital organs from this acidic waste，the body changes the acid into fat and stores it safely away from the organs．
Processed foods contain chemical elements，which might confuse the appetite mechanism that tells us when we've had enough to eat； as a result，people often overeat．Processed foods also upset the digestive cycle．The body will either identify these foods as allergens and then store them safely away from the organs as fat，or the remains of undigested food will become acidic and enter the bloodstream as acid waste，which will stick to the blood vessel walls and block the passage of vital oxygen and nutrients heading for the body's cells．The body's metabolism（新陈代谢） becomes inactive，and then result is weight gain and obesity．
The accumulation of acid in the digestive tract makes digestion increasingly inefficient．When that happens，even healthy foods can become acidic and the food allergies will become more common．
To stop this vicious（恶性的） circle in its tracks，people need to consume food and supplements that will neutralize （使…中和）the acid already accumulated in body．Eating the right types of raw and whole foods can help．It's also important to restore your enzyme balance．You need to identify and avoid the foods that cause acid accumulation and consume the foods that increase enzyme production．If you truly want to change and help your body heal itself，you need to take an active approach．
27．What is the main purpose of this passage？B
A．To tell the differences between raw and processed foods．
B．To advocate eating more raw and whole foods．
C．To inform people of the harm of processed foods．
D．To warn people of the problem of obesity．
28．It can be inferred from Para.2thatD．
A．it is essential for people to protect their vital organs
B．giving up cooked and refined foods is a new lifestyle
C．we'd better be cautious about raw and whole foods
D．foods with natural enzymes help people keep fit
29．Processed foods are unhealthy because theyB．
A．destroy body's cells
B．may lead to obesity
C．are difficult to digest
D．stop body's metabolism
30．What is likely to be talked about following the last paragraph？A
A．Suitable types of raw and whole foods．
B．Different causes of acid accumulation．
C．Correct ways to cook raw foods．
D．Active approaches to avoid acid．
31．What can we learn from the text？C
A．Processed foods are good for our appetite mechanism．
B．The accumulation of acid in the digestive tract makes digestion more effective．
C．Eating the right types of raw and whole foods does good to our body．
D．Processed foods also comfort the digestive tract．
