单项选择题
ANCHOR HAS ITS OWN CABLE TWISTED AROUND IT defines（）.
A.foul of anchor B.dropping anchor C.weighing anchor D.walking back anchor
单项选择题 （）sends a radio signal from the bottom of the ship to the sea-bed,from which it is reflected.
单项选择题 The ARPA may swap targets when automatically tracking if two targets（）
单项选择题 Vapor given off by a flammable liquid will burn when ignited provided（）
