At what point does a SART begin transmitting?

A、Itimmediatelybeginsemissionwhenplacedinthe“on”position.
B、Itmustbemanuallyactivated.
C、Ifithasbeenplacedinthe“on”position,itwillrespondwhenithasbeeninterrogatedbya9-GHzradarsignal.
D、Ifithasbeenplacedinthe“on”position,itwillbegintransmittingimmediatelyupondetectingthatitisinwater.