听一段对话，回答第 11、12 小题。
() 11. What does the boy's mum advise him to do with the old things?
A. Sell them online.
B. Throw them away.
C. Give them to friends.
() 12. Why does the boy want to keep the toy cars?
A. They are very expensive.
B. They are still new and useful.
C. They help him remember the old time.