What is the command sequence to configure an FXS port as a signal loop-start?

A.
router(config)# voice-port slot/port
router(config-voiceport)# signal loopstart
router(config-voiceport)# shutdown
router(config-voiceport)# no shutdown

B.
router(config)# voice-port slot/port
router(config-voiceport)# signal loopstart

C.
router(config)# voice-port slot/port
router(config-voiceport)# signal groundstart
router(config-voiceport)# shutdown
router(config-voiceport)# no shutdown

D.
router(config)# voice-port slot/port
router(config-voiceport)# signal groundstart