The sports meet, originally due to be held last Friday, finally ______ because of the terrible weather.

A．put off

B．broke down

C．called off

D．set off

对映异构体之间产生不同类型药理活性的药物是( )。

A．氯普噻吨
B．普萘洛尔
C．马来酸氯苯那敏
D．右丙氧芬
E．氯霉素