I am usually on time for school. I have never been late for my lesson. But this morning I was very late. At seven thirty this morning I was looking for my shoe. My right shoe was in my room, but my left shoe was missing. At seven forty five I was still looking for it. At eight o'clock my little sister was going past my door. Look! What was on her foot? My shoe! She was playing with it. I was half an hour late, but my teacher was not angry with me. She told me to hand in my exercise book. She looked very serious and asked me, "Why did you draw such a picture in your exercise book?" I hung down my head, and did not say a word. My little sister gave me much trouble.10. What is the writer's problem?
A. He is never late
B. He left his exercise book
C. He didn't do his homework
D. He missed his left shoe ​