如图所示，人在岸上拉船，已知船的质量为m，水的阻力恒为f，当轻绳与水平面的夹角为θ时，船的速度为v，此时人的拉力大小为F，则（   ）

补全对话

从方框中选择最佳选项完成对话，有两项多余

a. That's OK.

b. Because it is fast (快的) and easy.

c OK, then click "save" again.

d. I like it very much.

e. Yes, I have one.

f. How often do you use your computer?

g. What do you usually use your computer for?

A: Do you have a computer at home?

B: ____It's a birthday present from my uncle.

A:____

B: I usually use it to surf (冲浪) the Internet.

A: Why?

B:____

A:____

B: Every morning.

A: How do you like your computer?

B:____ It's very useful.