For FM position update, the following description is correct:

A、Duringaircraftinitialization,eachfmgcdisplaysthegpirsposition
B、Attakeoff,iftheGPSmasterisavailable,theFMpositionisupdatedtotherunwayheadpositioninthedatabase
C、Inflight,FMpositionapproachesGPSpositionorradioposition,andtheapproachratedependsonaircraftspeed