波形补偿器应严格按照管道中心线安装，不得偏斜，补偿器两端应设（）

A、至少一个导向支架；

B、至少各有一个导向支架；

C、至少一个固定支架；

D、至少各有一个固定支架。

For existing ships，（）is not an improvement to safety.

A.the reinforcement of the aft transverse watertight bulkhead

B.the double bottom structure in way of the foremost cargo hold

C.the introduction of a more rigorous survey regime and greater attention to operating procedures

D.introduction of new and improved designs