---I will have to think about it again．

--- If you _    , you may lose the opportunity to compete altogether．

A．hesitate

B．wonder

C．continue

D．fail

青霉素G水溶液不稳定，久置可引起的变化是( )

A．诱发过敏反应及中枢不良反应

B．药效下降

C．药效下降并诱发过敏反应

D．诱发过敏反应

E．诱发中枢不良反应