题目内容

Which of the sentences below best expresses the essential information in the highlighted sentence in paragraph 6？ Incorrect choices change the meaning in important ways or leave out essential information.

A. Before considering phytoremediation, hyperaccumulating species of plants local to the target area must be identified.
B. The investigation begins with an evaluation of toxic sites in the target area to determine the extent of contamination.
C. The first step in phytoremediation is the planting of hyperaccumulating plants in the area to be cleaned up.
D. Mines and irrigation ponds can be kept from becoming contaminated by planting hyperaccumulating species in targeted areas.

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Scientists have known for some time that certain plants, called hyperaccumu-lators, can concentrate minerals at levels a hundredfold or greater than normal. A survey of known hyperaccumulators identified that 75 percent of them amassed nickel; cobalt, copper, zinc, manganese, lead, and cadmium are other minerals of choice. Hyperaccumulators run the entire range of the plant world. They may be herbs, shrubs, or trees. Many members of the mustard family, spurge family, legume family, and grass family are top hyperaccumulators. Many are found in tropical and subtropical areas of the world, where accumulation of high concentrations of metals may afford some protection against plant-eating insects and microbial pathogens.
Why does the author mention "herbs," "shrubs," and "trees"？

A. To provide examples of plant types that cannot tolerate high levels of harmful minerals
B. To show why so many plants are hyperaccumulators
C. To help explain why hyperaccumulators can be found in so many different places
D. To emphasize that hyperaccumulators occur in a wide range of plant types

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The word "suspended" in the passage is closest in meaning to

A. grown
B. protected
C. spread out
D. hung

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According to paragraph 3, what is the advantage of hydroponics for research on nutrient deficiencies in plants？

A. It allows researchers to control what nutrients a plant receives.
B. It allows researchers to observe the growth of a large number of plants simultaneously.
C. It is possible to directly observe the roots of plants.
D. It is unnecessary to keep misting plants with nutrient solutions.

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The word "facilitates" in the passage is closest in meaning to

A. slows down
B. affects
C. makes easier
D. focuses on

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