What action might increase the radius of a load on the crane?

Increasing the radius of a load on a crane is achieved by extending the boom. When the boom is extended, the distance from the crane's pivot point to the point where the load is suspended increases. This change in position allows for the load to be placed further away from the crane, effectively increasing the working radius.

The other choices do not contribute to increasing the radius. Lowering the boom slowly would bring the load closer to the ground but does not affect the horizontal distance from the crane. Keeping the boom stationary means it remains at the same length and position, which does not change the radius at all. Therefore, extending the boom is the action that directly increases the radius of a load.