单项选择题
A.the letters ICW after the aid's number or letter
B.yellow stripes，squares，or triangles marked on them
C.white retroreflective material
D.the light characteristic and color for lighted aids
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?（）
单项选择题 After you enter the Ohio River at Cairo，which span of the Illinois Central RR Bridge would you select to pass under? （）