Final answer:
Ben's injury was not due to any of the provided options but was a result of a gunshot wound to his hand, which caused him to lose balance and fall.
Step-by-step explanation:
Based on the provided reference information, it appears that Ben was injured by putting his hand on a rock, which had been shot through, and subsequently he fell. As such, none of the options A) He fell from a ladder, B) He tripped over a cable, C) He hit his head on a beam, or D) He slipped on a wet floor are correct in the context of how Ben got hurt in Alex's basement. The detail provided points to an injury due to a gunshot wound followed by losing balance and falling, rather than an accident caused by an environmental factor in the basement like the choices suggest.