Fill in the blank with a suitable preposition.
The preposition ‘on’ is used to refer to something being carried or possessed by someone. In the given sentence the robbers let the person go as he didn’t carry any money with him. Therefore ‘on’ is an apt answer, so option B is correct. On the other hand ‘upon’ is generally used to speak about climbing on top of a moving object which is not the case here, hence option D is incorrect. The prepositions ‘at’ cannot be used in the given context because ‘at’ denotes a place. The sentence discusses a person and not a place hence option C is incorrect. The preposition ‘for’ is used to indicate for whom something is meant for. In the given sentence Rob is not a part of the robbers and is the victim, therefore the money cannot be intended ‘for’ him. Therefore we cannot use ‘for’ in the given context as it is illogical. Hence option A is incorrect.