线圈内感应电动势的大小和线圈内的变化率成正比

An area within coverage of Inmarsat geostationary satellites.
B. An area, excluding sea area Al, within coverage of Medium Frequency （MF） coastal radio stations in which continuous DSC alerting is available.
C. An area within coverage of VHF coast radio stations in which continuous DSC alerting is available.
D. The extreme polar regions

A group of ship stations.
B. A vessel operating in sea area A3.
C. A coast station.
D. A vessel