We should all remember that some great scientific discoveries _____________ by chance.
| A．gained | B．discovered | C．occurred | D．earned |
--- Would you care for a cup of coffee?
--- I ________ one. Thank you just the same.
| A．had | B．have had | C．would have | D．will have |
A certain percent of your salary is ________ by the employer as insurance payments.
| A．kept away | B．kept out | C．kept up | D．kept back |
--- Are you in a hurry?
--- No, in fact, I’ve got plenty of time. I _______ wait.
| A．can | B．may | C．must | D．Should |
You can’t appreciate happiness _______ you have known sadness too.
| A．because | B．when | C．though | D．unless |
We shouldn't have come north for Christmas vacation. If we _______, we wouldn't be stuck in the snow right now.
| A．wasn't | B．didn't | C．hadn't | D．weren't |