某市为推广先进生产经营管理模式，对效益最好的几个企业进行调查，此种调查属于（）。

A.重点调查

B.典型调查

C.整群调查

D.抽样调查

Upon hearing the abandon ship signal，you put on your life jacket and report to your station. After the cover is removed you board your open lifeboat boat. The FIRST thing to do is to（）.

A.release the gripes

B.release tricing pendants

C.put the cap on the drain

D.lift the brake handle