The correct answer is A. a cry in vain.
The phrase “cry in the wilderness” is a metaphor for a cry that is not heard or heeded. In this case, the speaker is saying that eloquent lamentations regarding the fate of the flora and fauna are likely to be ignored. This is because the people who are in a position to do something about the problem are more likely to be concerned with other issues.
Option B, an unpleasant situation, is not the correct answer because it does not capture the sense of futility that is implied in the phrase “cry in the wilderness.” Option C, a cry with a laughter, is also not the correct answer because it does not make sense in the context of the sentence. Option D, a laughter having no end, is also not the correct answer because it does not capture the sense of sadness and despair that is implied in the phrase “cry in the wilderness.”