Come and see me whenever_________.[ ]

A. you are convenient.      

B. you'll be convenient

C. it will be convenient to you.

D. it is convenient to you

立井井筒表土段采用冻结法施工时，其水文观测孔应该布置在（）。

A.井筒掘进断面内

B.井筒冻结圈上

C.井筒掘进断面外

D.井筒附近