— What did you do during your holidays?

— ______

A．Nothing much.

B．Nothing serious.

C．Nothing more.

D．Nothing interesting.

对烟囱、排毒塔等污染源进行环境监测与评价，其范围应是其几何高度的（）倍。

A.5～10倍

B.10～20倍

C.20～30倍

D.30～40倍

E.40～50倍