_______, or you’ll fail the exam.
A. Studying hard B. Study hard C. To study hard
We really don’t know _______. Could you help us?
| A．how to do | B．what to do |
| C．to do what | D．to do how |
—Will you please ________ do that? —OK, I won’t.
| A．won’t | B．not | C．don’t | D．can’t |
We had fun ________ the robots do many different kinds of things.
| A．to watch | B．watched | C．watching | D．watches |
The boss makes the workers ________ long hours every day.
| A．work | B．to work | C．works | D．working |
—________ will you come back from your work, Dad?
—In about half an hour, dear.
| A．How long | B．How often |
| C．What time | D．How soon |