It is often________that one trouble never comes alone.In my rush to leave I forgot to take the

plan I had made the night before.[      ]

A. to say    

B. saying    

C. said  

D. being said

庆大霉素与速尿合用时可引起

A．肾毒性加重

B．肾毒性减轻

C．抗菌作用增强

D．耳毒性加重

E．利尿作用增强