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?（）

A.Thimble Shoal Main Channel or the South Auxiliary Channel
B.Any of the channels but keep to the right hand side
C.The South Auxiliary Channel
D.Thimble Shoal Main Channel

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? （）

A.Any span is navigable
B.Northbank or Southbank
C.Southbank span only
D.Northbank span only

单项选择题After you enter the Ohio River at Cairo，the Map shows that the deepest water under the Illinois Central RR Bridge would be found under which span? （）

A.Right Descending Bank span
B.Left Descending Bank span
C.Center span
D.Water is equal under all spans

单项选择题After the passage of a cold front the visibility（）.

A.does not change
B.improves rapidly
C.improves only slightly
D.becomes poor

单项选择题After the initial cleaning of flue gas in an inert gas system the gas is passed through what device for final cleaning?（）

A.Scrubber
B.Demister
C.Deck water seal
D.Final filter