Hi, as I           soon for Nicaragua to do some research, I would love to hear your suggestions.

A．am leaving

B．am left

C．was leaving

D．was left

为保证生产安全，根据《公路法》规定，改建公路时，施工单位应当在施工路段两端设置明I的施工标志、（）标志。

A.防尘

B.安全

C.防盗

D.防火