Answer: b) It conveys the idea that of trees losing their leaves and making noises in the wind.
Step-by-step explanation: personification is when the author gives human characteristics to non human objects (like the trees going to sleep or whispering), in this excerpt, when the author says that the trees are disrobing, he's referring to them losing their leaves, and when it says that the trees are having little bed-time conferences and whisperings and good-nights, he is referring to the noises the trees make in the wind.