1£®(ºþÄϾí)If nothing ____________(do), the oceans will turn into fish deserts.

´ð°¸£ºis done

2£®Before you leave the classroom£¬the door and windows should ____________(close) in case of rain.

´ð°¸£ºbe closed

3£®Every possible means ____________(try) by the company to improve its production.

´ð°¸£ºhas been tried

4£®The car which is under repair____________(belong) to Mr Green.

´ð°¸£ºbelongs

5£®There’s a crowd of people over there. Go and see what ____________(sell)£®

´ð°¸£ºis being sold

6£®Over the past few years, a large number of houses ____________(build) for the low­income families.

´ð°¸£ºhave been built