Explanation
Correct answer: A.
Choice A is the best answer because it best states the main idea of the text. The speaker describes an evening scene observed from a boat: "little lights in little ports come out" and are reflected in the water’s surface "with the stars," fishing boats are moored, "sails are furled" (rolled up), and the riding-light is shining. The speaker emphasizes the calmness of the scene, noting that the "race of wind is stilled" and the atmosphere is sleepy ("slumbrous waters pool a slumbrous world"), and then indicates that the calmness prompts thoughts of how old age might be "sweet" and "quiet" and "gracious in retreat" after "a windy youth" with "storms." Thus, the main idea is that the tranquility of a port in the evening can lead a person to appreciate the potential stillness of old age.
Why the other choices are wrong
Choice B
Choice B is incorrect because the speaker isn’t discussing the difficulty of bringing a ship into port but describing the calmness of the port at night. And rather than suggesting that old age involves struggles, the speaker suggests that after "a windy youth" with "storms" to be weathered, old age will be "sweet," "quiet," and "gracious"—that is, old age will be tranquil like a port at night.
Choice C
Choice C is incorrect because the speaker isn’t suggesting that a person who has lived a varied and active life might find it difficult to stay in a calm place in old age. On the contrary, the speaker suggests that after a "windy youth" with "storms," old age can be welcomed as something "sweet," "quiet," and "gracious," just like a calm port at night.
Choice D
Choice D is incorrect. Although the speaker does touch on the idea of a "windy youth" followed by "sweet old age," the speaker doesn’t tie that idea to a contrast between daytime activity and nighttime peacefulness at a port. The speaker doesn’t address any activity during the day at a port, only briefly mentioning that the "race of wind is stilled" at the end of the day, and instead focuses on the tranquility of the port at night and how it prompts thoughts of "quiet" and "gracious" old age.