.It was not until he went abroad for further study______Li Ming realised the importance of English.

A．when

B．that

C．where

D．before

下列船舶中（）在作业所必需的限度内可免受通航制条款的约束。

A.从事捕鱼的船舶

B.从事敷设、维修或起捞海底电缆的船舶

C.从事清除水雷的船舶

D.B、C都是