题目

Why do men die earlier than women? The latest research makes it known that the reason could be that men’s hearts go into rapid decline（下降） when they reach middle age. The largest study of the effects of ageing on the heart has found that women’s longevity may be linked to the fact that their hearts do not lose their pumping power with age. “We have found that the power of the male heart falls by 20-25 percent between 18 and 70 years of age,” said the head of the study, David Goldspink of Liverpool John Moores University in the UK. What surprises scientists is that the f下列对生物种群的叙述，哪个正确A.种群是生态系的最基本组成单元B.基因同质化将可能导致种群的灭绝C.若没有天敌，种群将无限制的成长D.一个种群可以由一个物种或是好几个物种共同组成