Question

why should you chock (block) the wheels of a tractor - trailer before loading or unloading?
the trailer could move away from the loading dock.
the dock board may not fit between the loading dock and trailer.
the wheels do not need to be chocked.
the lift truck could go through the floor of the trailer.

Explanation:

Chocking wheels prevents trailer movement. Without chocks, trailer could roll away during loading/unloading. Dock board fit and lift - truck floor issues are unrelated. Wheels need chocking for safety.

Answer:

The trailer could move away from the loading dock.