Question

Of all excavation hazards, _______ poses the greatest risk.

a. a cave-in
b. inhalation
c. moving machinery

Answer 1

Of all excavation hazards, a cave-in poses the greatest risk of all. This could be fatal to a worker. The correct answer is A, a cave-in. 

Answer 2

Of all excavation hazards, A. a cave-in possesses the greatest risk.
When there is a cave-in, the walls of a cave crumble and may close the exit of the cave, thus preventing workers from leaving it safely. Rocks may also fall from the ceiling and injure, if not kill somebody.