单项选择题
Air circulation is caused or affected by（）.
A.the rotation of the earth on its axis B.convection currents caused by differences in radiant heating between equatorial and polar regions C.mountain ranges D.All of the above
单项选择题 Aids to navigation marking the intracoastal waterway can be identified by（）.
单项选择题 After you get underway，what is the first river gage you will pass? （）
单项选择题 After you enter Thimble Shoal Channel，you will alter course to pass between Trestle “A” and “B”. Which channel should you use?（）
