整体壁板制造工艺的优点：（）。

A、简化互换协调

B、减少工装与装配量

C、缩短周期、提高效率

D、提高强度与刚度

Distress flares and smoke signals for small passenger vessels（）.

A.are not required aboard vessels on runs of less than 30 minutes duration

B.must be Coast Guard approved and stowed in a portable，watertight container

C.must be marked with an expiration date not more than 42 months from the date of manufacture

D.All of the above