单项选择题

By saying these figures are conservative (Line 1, Paragraph 3), Dr Worm means that ______.

A．fishing technology has improved rapidly
B．the catch- sizes are actually smaller than recorded
C．the marine biomass has suffered a greater loss
D．the data collected so far are out of date

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单项选择题

We can infer from Dr Myers and Dr. Worm's paper that ______.

A．the stock of large predators in some old fisheries has reduced by 90%
B．there are only half as many fisheries as there were 15 years ago
C．the catch sizes in new fisheries are only 20% of the original amount
D．the number of larger predators dropped faster in new fisheries than in the old

单项选择题

The extinction of large prehistoric animals is noted to suggest that ______.

A．large animal were vulnerable to the changing environment
B．small species survived as large animals disappeared
C．large sea animals may face the same threat today
D．slow - growing fish outlive fast - growing ones