You are approaching an open drawbridge and sound the proper signal. You receive no acknowledgment from the bridge. Which action should you take?

A
Approach with caution and proceed through the open draw.
B
Approach under full control to a position no closer than 400 yards from the bridge and await a signal from the bridge.
C
Hold in the channel as a vessel is closing the bridge from the other direction.
D
Resound the opening signal and do not pass through the bridge until signals have been exchanged.
E