Question

The vegetable broccoli has a natural substance(物质)that may prevent some kinds of cancer． 　　Recently, American scientists reported that not all broccoli is equal in fighting cancer．The scientists examined different kinds of broccoli plants．They attempted to activate(激活)an enzyme(酶)in the plants that may protect against some cancers． 　　The scientists discovered major differences among the broccoli tested．Some plants had very little of the cancer-fighting substance．Other plants had large amounts of the substance．The Journal of the American Society for Horticultural Science(园艺学)published the findings． 　　Early studies have shown that people who eat vegetables like broccoli have lower rates of colon(结肠)and rectal(直肠)cancers．Broccoli plants and young seedlings(苗)have a chemical called glucoraphanin．They also contain a product of the chemical, called sulforaphane．Sulforaphanin causes the production of enzymes that slow the growth of cancer tumors(肿瘤)in laboratory animals． 　　Scientists at Johns Hopkins University in Baltimore, Maryland discovered the cancer fighting agent in broccoli nine years ago．Johns Hopkinns scientists joined with the United States Agricultural Research Service to organize the new study．A few years ago, the Research Service’s Vegetable Laboratory in Charleston, South Carolina grew more than seventy kinds of broccoli．The scientists then examined the chemicals each plant． 　　They observed extreme differences in glucoraphanin levels and the activity of enzymes in the broccoli tested．Some kinds of broccoli had very small amounts of the chemical．However, others had levels about thirty times greater． 　　Scientists want to learn more about the different levels of glucoraphanin and sulforaphane in broccoli plants．They hope new kinds of broccoli with the greater levels of the protective substances．They say eating such improved broccoli might result in more effective, natural defenses against cancer． 　　American doctors say eating fruits and vegetables, including broccoli, is important for health． 　　The National Cancer Institute says people should eat at least five servings(份)of fruits and vegetables everyday． (1) This passage is to report the recent finding that ________． [　　] A． eating broccoli helps prevent cancer B． people who eat vegetables like broccoli are at lower risk of getting cancer C． eating some kinds of broccoli defend people against some cancers D． not all broccoli plants are equally valuable as a cancer-fighting vegetable (2) Some American scientists are going on with their study on broccoli in order to ________． [　　] A． discover the kind of broccoli that has the highest levels of the cancer-fighting substance B． find out why the rates of some cancers are low among broccoli eaters C． develop improved broccoli that will be even more effective in fighting cancer D． produce more of the protective substances glucoraphanin and sulforaphane (3) The scientists mentioned in the passage have done all the following EXCEPT ________． [　　] A． eating broccoli to test its effect B． growing all kinds of broccoli C． feeding a variety of broccoli to some animals like rats and mice D． looking for the protective substance in broccoli (4) In which state is the famous John Hopkins University located? [　　] A． Baltimore． B． Maryland． C． Charleston． D． South Carolina．

Answer 1

答案：1．D;2．C;3．A;4．B;