阅读下面的短文，从短文后所给的四个选项中，选出可填入空白处的最佳选项。
Benjamin is the unluckiest boy in the world. He 1 falls ill(生病), but if he falls ill, it is on the weekend. He is a good student, but when he takes a test, his pen 2 . His bird sings very well, but when he asks 3 to listen to it, the bird becomes silent(沉默的).
But Benjamin thinks he is 4 boy in the world. He has wonderful parents and a lovely sister. He has a singing bird. His classmates are friendly to 5 . Benjamin is always happy and he is kind.
One day his mother 6 him some money to buy an ice-cream. When he 7 the ice-cream shop, he saw an old man outside it. He had old clothes, terrible glasses, and he looked 8 . Benjamin thought he was poor. He decided 9 the ice-cream and gave the money to the man.
"Thank you. You are a kind boy. But I' m not poor. Keep your money, I'm the richest man in town and sometimes I wear old clothes to see 10 people do," the man said and gave the money 11 to him.
The man took Benjamin to the biggest 12 in town and said, "Choose 13 you like. I can buy you the most expensive one." Benjamin asked, "Can I choose 14 ? "Of course," answered the man.
Benjamin chose the newest radio because when his bird keeps silent, he can at least listen to it with his friends. He then bought a new pair of glasses 15 the man.
合成 
．（部分试剂和反应条件已略去）
②若
④