（）is not a type of tide.

Water may boil up around the stern of a vessel in a channel due to（）.

A.slack water when upbound
B.shallow water
C.a cross current
D.a head current

点击查看答案&解析

Tropic tides are caused by the（）.

A.Moon being at its maximum declination
B.Moon crossing the equator
C.Sun and Moon both being near 0°declination
D.Moon being at perigee

点击查看答案&解析