【单选题】Which one of the following statements concerning COSPAS-SARSAT is true?
A.
EPIRBs are units that are used as alerting devices.
B.
There are satellites in a low-earth polar orbit that detect EPRIB beacons on 406 MHz and relay the information to an earth-side Local User Terminal (LUT).
C.
the Doppler frequency measurement concept is used to determine the EPIRB’s location.