Explanation
Correct answer: A.
Choice A is the best answer because is accurately states the main purpose of the text. The text begins by declaring that although a song is "but a little thing," or seemingly insignificant, singing it brings joy and gives the speaker of the text "zest," or excitement, in "hours of toil." The remainder of the text explores the idea that as night is falling, singing allows the speaker to feel that "all is well." Thus, the main purpose of the text is to convey how engaging in song makes the speaker feel.
Why the other choices are wrong
Choice B
Choice B is incorrect. Although the text mentions a shepherd, it neither indicates that the shepherd is singing nor does it compare the shepherd to the speaker.
Choice C
Choice C is incorrect. The text indicates that the speaker works hard, engaging in "hours of toil," and it can be inferred that the speaker likely lives in a rural area, since cows and a cowbell can be heard nearby. However, the text does not suggest that the speaker is a farmer or feels excited about farming. Moreover, the shepherd in the text is not a literal reference to someone who herds sheep but instead a figurative description of the moon as the shepherd of the stars.
Choice D
Choice D is incorrect because in the text, the speaker is singing a song, not listening to others sing one. Moreover, the text describes the feelings that the speaker has when singing a song, not the song itself.