Many people enjoy _______ the CD ________ Heart Strings.

A．to hear, calling

B．to listen to, calling

C．hearing, called

D．listening to, called

可获得最大未观察到有害作用剂量的毒性试验是

A．急性毒性试验
B．亚急性毒性试验
C．致畸试验
D．慢性毒性试验
E．蓄积毒性试验