根据短文理解, 从A、B、C三个选项中选择最佳答案填空。
    Billy is a boy of fifteen. His parents 1 three years ago. One day when he was walking in the street, he found a wallet. He 2 it to the owner, Mr. Baker. Mr. Baker gave his thanks to the boy. As the boy had no job, Mr. Baker made him 3 for him in his factory. Billy worked so 4 that Mr. and Mrs. Baker were happy with him.
    Mr. Baker loved planting trees. The week before last, he 5 a few trees home,   planted them in the garden himself and watered them every day. Several days 6, he had to leave for another city. 7 he started, he said to Billy. "Take good care of the trees. Some boys near our house always want to steal 8." "Don't worry about them, sir." answered Billy, "I'll try my best 9 them." Six days passed and Mr. Baker came back. He asked, "Has anyone ever come to steal the trees?" "No, sir." said Billy, "To stop someone from 10 the trees, I pulled them up six days ago. I have hidden them for almost a week!"