问题：

[单选] How can rescue personnel detect that a SART is transmitting in the immediate vicinity?（）

A . The SART's blips on the PPI will begin arcing and eventually become concentric circles
B . The DSC unit will react to the SART's signal and respond with the two-tone alarm
C . The SART can provide an approximate location to within a two nautical mile radius，per IMO standards
D . The SART signal appears as a target which comes and goes; the effect of heavy swells on a SART