According to Paragraph 4, Caulerpa taxifolia is known as "killer algae" because
A. it has colonized a variety of underwater environments.
B. it eliminates native plants and drives away native animals.
C. it is toxic to people who come into contact with it.
D. it grows too deep for other species to reach it.
查看答案
According to Paragraph 6, one similarity between primary and secondary groups is that they
A. give rise to technological development.
B. are absent in less-developed nations.
C. can be observed in all kinds of societies.
D. are essential to the health of societies.
What determines the price of a goods in a market economy？
A. The cost of all elements of its production.
B. The cost of not making other goods.
C. The efficiency of the manufacturing process.
D. The quantity of material supplied.
According to Paragraph 6, why is manual uprooting a difficult process？
A. It requires divers to undergo strenuous training.
B. The algae's roots are usually too strong to pull out.
C. It is necessary to remove every last piece of algae.
D. The algae grow back faster than they can be removed.
The word affords in the passage is closest in meaning to
A. lends.
B. provides.
C. costs.
D. teaches.
微信支付 
支付宝支付