— Mom, what did your doctor say?

— He advised me to live _____ the air is fresher. [ ]

A. in where

B. in which

C. the place where

D. where

按照周期波动时间的长短划分，经济周期类型有（）。

A.朱格拉周期

B.库兹涅茨周期

C.哈罗德周期

D.康德拉耶夫周期

E.基钦周期