When a marine surveyor is employed to assi

问题：

When a marine surveyor is employed to assist in the move of a mobile offshore drilling unit，he（）.

A.becomes responsible for the safe movement of the rig

B.relieves the Offshore Installation Manager at the moment the rig is free from the bottom

C.must be designated as the person in charge of the rig

D.is a specialist who is hired to provide advice and guidance on aspects of the move