According to scientists, our mental abilities begin to ___ from the age of 27 after reaching the highest level at 22.
| A．differ | B．shrink | C．fail | D．decline |
The students entered the classroom，smiling and________，and ______ down to have their lessons.
| A．talked；sat | B．talking；sitting |
| C．talking；sat | D．talked；sitting |
He kept a little notebook, in which the names and addresses of his friends.
| A．wrote | B．was writing |
| C．were written | D．was written |
that her mother would come back soon, the girl calmed down.
| A．Having convinced | B．Being convinced |
| C．Convincing | D．Convinced |
—Why? Tom,your skirt is so dirty!
—Mum, I my storeroom downstairs.
| A．cleaned | B．have cleaned |
| C．was cleaning | D．have been cleaning |
I’m sure you will do better in the test because you so hard this year.
| A．studied | B．had studied |
| C．will study | D．have been studying |