—Do you think playing cards is beneficial to our study?

—No，if ________，it can help us kill time when we have nothing to do.

A．something　　　　

B．anything

C．nothing

D．everything

延胡索镇痛的活性成分是

A．延胡索甲素
B．延胡索乙素
C．延胡索丙素
D．延胡索丁索
E．延胡索戊素