假如你是Xiao Dong，Xiao Liang给你来了一封信，请你根据信的内容写一封回信。信的开头已给出，请把信补充完整。
Dear Xiao Dong,
I like your programs very much. I’m writing to ask you something about American social customs. My American friends want me to join them in their dinner party. I’m very happy and have decided to go, but I’m a bit worried about it. The social customs in my country are different from there, so I’m afraid of making some mistakes.
Should I bring a present, such as sweets or flowers? Should I arrive on time or a bit late? At the dinner table, how can I use fork and knife? How can I let the family know that I’m thankful for their  kindness.
Yours’
Xiao Liang

--Can I use your mobile phone?
--Of course.           .

—Excuse me, Maria. Can I use your bike?

—Sure. Here you are. But you must return it _____ time.

A. inB. atC. on D. to

—Excuse me, Maria. Can I use your bike?

—Sure. Here you are. But you must return it _____ time.

A. inB. atC. on D. to