A Class S EPIRB is a（）.

A.is primarily designed for vessels operating up to 50 miles offshore or on foreign waters
B.transmits a signal that can be detected by satellite
C.must be manually activated
D.operates in the medium and low frequency bands

A.approved by the CCS
B.designed for float free，automatic activation
C.operated on 121.5/243 MHz
D.operated manually

A.a safety line attached to a man working over the side
B.used to measure water depth
C.used to slow the headway of a barge
D.used to measure the overhead height of a bridge