单项选择题
On the high seas，a fog signal consisting of one prolonged blast followed by four short blasts would indicate the presence of a（）.
A.vessel being towed B.fishing vessel engaged in trawling C.vessel at anchor warning you of her location D.power-driven pilot vessel on station underway
单项选择题 On the approach of a warm front the barometric pressure usually（）.
单项选择题 On a nautical chart，the inner ring of a compass rose indicates（）.
单项选择题 Navigational warnings are published according to（）.
