The population of elephant seals, reduced by hunting to perhaps a few dozen animals early in this century, has soared under federal protection during the last few decades. However, because the species repopulated itself through extensive inbreeding, it now exhibits a genetic uniformity that is almost unparalleled in other species of mammals, and thus it is in far greater danger of becoming extinct than are most other species.
Given the information in the passage above, which of the following is most likely the reason that other species of mammals are leas likely than elephant seals to become extinct ？（）

A．Other species of mammals have large populations, so the loss of a few members of the species is not significant.

B．Other species of mammals have increased their knowledge of dangers through the experience of generation after generation of animals.

C．In other species of mammals, hunters can readily distinguish between males and females or between young animals and adults.

D．In other species of mammals, some members of the species am genetically better equipped to withstand a disease or event that destroys other members of the species.

E．Other species of mammals have retained habits of caution and alertness because they have not been protected as endangered species.

叩诊的注意事项之一是（）

A.先叩正常牙，后叩患病牙齿

B.用器械的尖头工作端做叩诊

C.力量按从大到小的顺序进行

D.方向和牙长轴垂直查根尖部

E.方向与牙长轴一致查根周部