____several times，but unfortunately，the boy still couldn’t smooth away the problem on his own.

A．Having been explained

B．The problem having been explained

C．The problem had been explained

D．Although the problem had been explained

旁站监理人员实施旁站监理时，若发现其施工活动已经或者可能危及工程质量的，应当及时向( )报告，由总监理工程师下达局部暂停施工指令或者采取其他应急措施。

A．监理工程师

B．总监理工程师

C．企业领导

D．监理工程师或总监理工程师