What is a "PAPI"(Precision Approach Path Indicator)?

A、Aninstrumentalaidthatprovidesguidanceinformationtohelpapilotacquireandmaintainthecorrectapproachtoanaerodromeoranairport
B、Avisualaidthatprovidedguidanceinformationtoheloapilotacquireandmaintainthecorrectdeparturetrackwhendepartingfromanaerodromeoranairport
C、Avisualaidthatprovidesguidanceinformationtohelpatowercontrolleracquireandmaintainthecorrectapproachtoanaerodromeoranairport
D、Avisualaidthatprovidesguidanceinformationtohelpapilotacquireandmaintainthecorrectglidepathtoanaerodromeoranairport