陈向东书中的一道题

mdjsabrina

Fossils of the coral Acrocora palmata that date from the last period when glaciers grew and consequestly spread from the polar regions are found at ocean depths far greater than those at which A. plamata can now survive. Therefore, all though the fossilized A. palmata appears indistinguishable from A. Palmata now living, it must have differed in important respects to have been able to live in deep wate.

The argument depends on the assumption that:

A. no fossils of the coral A palmata have been found that date from periods when glaciers were not spreading from the polar regions

B. geological disturbances since the last period during which glaciers spread have cuased no major downward shift in the lacation of A. palmata fossils

C. A. palmata now live in shallow waters in most of the same geographical regions as those in which deep-lying A. palmata fossils have been found

D. A. patmata fossils have been found that date from each of the periods during which glaciers are know to have spread from the polar region

E. A. palmata can live at greater depths where the ocean temperature is colder than they can where the ocean temperature is warmer.

The answer is B. But why?  Thanks a lot!

weiyu

B does rule out another possibility that the disturbance not the natural habitat breeds the difference.