—May I ask a question after class，Sir?

—       , but not during my lunch break.

A．I am sorry

B．Anytime

C．Go ahead

D．Certainly

钻孔灌注桩施工，孔深达到70m时，宜选用（）造孔。

A.冲击锥

B.冲击钻机

C.回旋钻机

D.潜水钻机