19世纪30年代，达尔文在环球考察中发现，不同品种的动物整体形态相似，属于相近的物种，但各具特点，距离越远，差异越明显。由此他认为生物进化的机制是（）

A.主动选择

B.人工选择

C.被动选择

D.自然选择

Last year the annual premium on a certain hospitalization insurance policy was $408, and the policy paid 80 percent of any hospital expenses incurred. If the amount paid by the insurance policy last year was equal to the annual premium plus the amount of hospital expenses not paid by the policy, what was the total amount of hospital expenses last year ？（）

A．$850.00

B．$680.00

C．$640.00

D．$510.00

E．$326.40