Although the causes of cancer ________, we do not yet have any practical way to prevent it．
| A．have uncovered | B．have been uncovering |
| C．are uncovering | D．are being uncovered |
The poem is hard to understand. Can you make ___ of it?
| A．idea | B．knowledge | C．sense | D．understanding |
–You are Mr. Zhang, aren’t you?
--______.
| A．Absolutely | B．Naturally | C．Normally | D．Completely |
I have ___all my papers but I still can’t find my notes.
| A．looked through | B．looked for | C．looked after | D．looked out |
We elected him ___ monitor of our class, and he gave ___ to everyone.
| A．a, respects and help | B．/, his respects and help |
| C．the, respect and honors | D．/, thanks and helps |
In general， the old man is generous. But ____， he was mean to an old beggar.
| A．at once | B．once again | C．for once | D．once over |