While listening in class, you should concentrate ____ your teacher.
| A．at | B．to | C．for | D．on |
相关试题
I didn't sleep well because_ suddenly knocked on the door just now.
| A．somebody | B．nobody | C．anybody | D．everybody |
They're shoes with _ . People can use them for seeing in the dark.
| A．letters | B．lights | C．wheels | D．colors |
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