单项选择题
An all-round flashing yellow light may be exhibited by a(n)（）.
A.vessel not under command B.air cushion vessel in the nondisplacement mode C.vessel towing a submerged object D.vessel engaged in diving operations
单项选择题 All fog signals shall be sounded every two minutes with the exception of a vessel（）.
单项选择题 According to the Rules，when should lights be displayed?（）.
单项选择题 A vessel towing where the tow prevents her from changing course shall carry（）.
