The correct option is
B would
According to the given statement, it states about the condition of life if there were no water, which is
indicating the consequence of an imagined event or situation, hence option B is the correct answer, as “would” is used to indicate the consequence of an imagined event. Option A is incorrect because “may” is used in the present tense, to talk of the correct present only, but the statement signifies something that was to exist from the past (life) hence incorrect.
Option C is incorrect because here in this statement, the absence of water speaks of consequences from the past, and the present, and possibly the future but not just the future, while “will” is used in future tense only. Hence incorrect.
Option D is incorrect because “could” is the past tense of “can” which expresses ability, which is incorrect.