The poem states: the wet stones glistening like sleepy crocodiles, the dry ones shaven water-buffaloes lounging in the sun. Hence wet stones are compared to crocodiles and dry stones to water buffaloes. The order in the options matters, so the correct pairing is crocodiles and water buffaloes.
Note: The NTA question has a grammatical slip (compared instead of compared to); we have read it as asking what the two stone types are likened to.