（）is taken from the lower most point o

1、The lower section of a piston is calle

The lower section of a piston is called the （）.AlandBskirtCcrownDplate

2、which function is the most important o

which function is the most important one of the GMDSS.（）AalertingBon-scene communicationCsafety informationDgeneral communicatio

3、What is the distance from the bottom o

What is the distance from the bottom of a wave trough to the top of a wave crest?（）AWave lengthBWave heightCWave breadthDwave depth

4、In the past, films were mostly taken _

In the past, films were mostly taken ______.A in a workshopB in the openC along the seasideD in the studio

5、A peculiarly pointed chin is his most

A peculiarly pointed chin is his most memorable facial（）AmarkBfeatureCtraceDappearance

6、Ullage measurements are taken from the

Ullage measurements are taken from the top of the liquid to（）.Athe base of the expansion trunkBthe base of the ullage portCa line scribed within the ullage portDan above-deck datum，usually the top of the ullage hole