On summer nights, we often go to sleep ____ the window open.[ ]

The 2010 Guangzhou Asian Games will be ________ from Nov. 12 to Nov. 27.

Excuse me, Mum. When can we have dinner? —Not until itin half an hour.

The air in Rizhao is getting much _____ now than a few years ago .

Here’s a watermelon. Please ____________.