—What can we do to________ bird flu from spreading?
—Try not to buy or eat chickens that have not been checked.
A. prevent B. cause C. discover
The new supermarket ______________ two years ago.
| A．built | B．builds | C．is built | D．was built |
Mary _________ as a volunteer teacher for 10 years.
| A．works | B．will work | C．worked | D．has worked |
— Is Mike at home?
— No. He ________ with his friends now.
| A．swims | B．is swimming | C．swam | D．will swim |
I will tell you the good news as soon as you _______ back.
| A．come | B．came | C．are coming | D．will come |
My grandma ______ dinner when I got home yesterday.
| A．cooks | B．will cook | C．is cooking | D．was cooking |