完成对话。
A: Hello !
B: Yes . What’s up ?
A:Could I borrow your bike again ?
B: Certainly .Has your bike been broken again ?
A: No . I’ve lost my key to the bike . But I have to go to see a friend .
B: I see .
A: About four o’clock .
B: OK . Here is the key .
A:
B: Bye !