单项选择题
A “full service” Loran-C receiver will provide（）.
A.matching pulse rates of at least 20 stations B.an automatic on-and-off switch C.a horizontal matching of all delayed hyperbolic signals D.automatic signal acquisition and cycle matching
单项选择题 A “figure eight” knot is used to（）.
单项选择题 A “fifteen-pound” CO2 extinguisher is so called because（）.
单项选择题 A “check” line is（）.
