Scientists say it may be one year or so ________ it is possible to test the new medicine on human patients

Some people waste a lot of food ________ others haven’t enough to eat

Jack，you look tired today.What’s wrong — I was _______busy _______ I didn’t go to bed until midnight yesterday.

The playground is behind the sports hall. We can say the sports hall is ___ the playground.

“Please close the window,” he said to me. He me the window.