Please explain answer choices

Hi, we are looking to prove that there are as many or more trees in S as there are in M. A does not do this, the total number of trees depends on far more factors than just the number planted in the last two years. B does exactly this. If M is entirely in S, then every tree in M is also in S, so M cannot have more trees than S. C does not prove anything, perhaps the epidemic is occurring in both cities. D also proves nothing, annual rainfall is only one factor impacting tree population E only tells a half the story, it is possible that more trees are planted to make up for the increase in trees cut down.