单项选择题
A.L B.N C.T D.Z
A signal indicating Greenwich mean time would be preced...
单项选择题A signal indicating Greenwich mean time would be preceded with（）.
A.a code hoist to indicate Greenwich mean time to follow B.the letter G C.the letters GT D.the letter Z
A sign of thunderstorm development is a cumulus cloud（）...
单项选择题A sign of thunderstorm development is a cumulus cloud（）.
A.darkening，growing in size and forming an anvil top B.that shows extensive vertical development C.creating cold downdrafts that are felt on the ground D.All of the above
A shipmate suffers a heart attack and stops breathing. ...
单项选择题A shipmate suffers a heart attack and stops breathing. You must（）.
A.administer oxygen B.immediately check his pulse and start CPR C.make the victim comfortable in a bunk D.immediately give a stimulant，by force if necessary
