But for friction (摩擦力), people ______ neither walk, nor even stand up.
| A．can | B．were able to | C．will be able to | D．could |
—Shall we go out for dinner tonight?
—______.
| A．You are right | B．It must be funny |
| C．That sounds great | D．Have a nice time |
--- Can you show me Mr. Jaffer’s office, please?
--- _____. But I don’t know if he is in at the moment.
| A．Thanks | B．Go on | C．Sure | D．You are welcome |
–The floor is dirty. Can anyone clean it?
–_____I do it all the time.
| A．Don’t mention it. | B．Why you? | C．Not sure | D．Not me again. |
—Sorry, I made a mistake again.
— ______. Practice more and you’ll succeed.
| A．Never mind | B．Certainly not |
| C．Not at all | D．Don’t mention it |
– Would you like to join us in the game?
–_____, for I have something important to attend to.
| A．I will | B．I’d love to |
| C．I won’t | D．I’m afraid not |