一Why are you ready ________ Jour study in America?

一Because English is spoken ________ the first language there. [ ]

A. to; by

B. for; as

C. to; as

D. for; by

中央空调闭式循环冷冻水系统日常水质管理的工作目标主要是防止（）。

A.结垢

B.腐蚀

C.污物沉积

D.菌藻滋生