（）is formed when the droplets or ice crystals in clouds have become sufficiently large to fall to the ground.

A.Humidity
B.Temperature
C.Precipitation
D.Wind

A.NAVETEX receiver
B.Search and Rescue Transponder
C.Emergency Position Indicating Radio Beacon
D.Digital selective calling

A.NAVETEX receiver
B.Search and Rescue Transponder
C.Emergency Position Indicating Radio Beacon
D.Digital selective calling