A、Because he was ill. B、Because he was rather weak. C、Because he was always afraid. D、Because she loved him. D

Mrs. Robinson had one small, son. His name was Billy. Mrs. Robinson loved Billy very much, and as he was not a strong child, she was always afraid that he might get ill, so she used to take him to the best doctor in the town four times a year to be examined.
    During one of these visits, the doctor gave Billy various tests and then said to him, "Have you had any trouble with your nose or ears recently?"
    Billy thought for a second and then answered, "Yes, I have." Mrs. Robinson was very worried. "But I’m sure you’ve never told me that, Billy!" she said anxiously.
    "Oh, really?" said the doctor seriously. ,And what trouble have you had with your nose and ears, my boy?"
    "Well" answered Billy, "I always have trouble with them when I’m taking my sweater off, because the neck is very tight."