Which one of the followings does not limit the effective range of radar（）.

A.Radio communications allow the crane operator to disregard the use of hand signals
B.The crane operators and signalman must be familiar with the correct hand signals
C.The forward cranes can be operated from the bridge
D.The aft cranes can be operated from the aft steering station

A.AIS is a global tracking system that relies upon INMARSAT C service to communicate vessel position and other safety related information to similarly equipped vessels，aircraft and shore stations within the area
B.AIS is a short-range 3 cm X-band radar system that automatically sends a vessel's position and other safety related information to similarly equipped vessels，aircraft and shore stations within the area
C.AIS is a short-range VHF-FM system that automatically broadcasts a vessel's position and other safety related information frequently to similarly equipped vessels，aircraft and shore stations within the area
D.AIS is a one-way centrally managed system that requires the local VTS to send commands to instruct each vessel to broadcast position and other safety related information to similarly equipped vessels，aircraft and shore stations within the area