— How heavily it rained this early morning.

— Yes. But            of the students in our class was late for school.  [ ]

A. some

B. none

C. all

采用冻结法施工，井筒的开挖时间要选择适当，当（）时最为理想。

A.冻结壁已形成又尚未冻至井筒范围以内

B.冻结壁已形成井筒范围以内

C.冻结壁即将形成

D.冻结壁尚未形成