根据对话内容，在每个标有题号的空白处填人一个适当的句子，使对话完整、合乎情景。

A: Be quick, Betty. Your uncle is waiting for you at the school gate.

B: My uncle? No, I don't have an uncle.

A:       小题1:    ?

B: He is my grandpa.

A: Really? But he looks so young.      小题2:     ？ 

B: He is 61.

A: Why is he waiting for you?

B: Today is my grandma's birthday. I will help my grandpa buy some presents for my grandma.

A: Did they buy presents for each other in the past?

B:     小题3:     . They usually bought very special presents for each other.

A:     小题4:   ？

B: They got married in 1976.

A: Does your grandpa still work?

B:     小题5: . He retired (退休) last year.

已知∠α=72°15′，则∠α的余角是（　　）

A．17°15′

B．17.75°

C．107°40′

D．无法确定