31.  We should open all the windows, so we don't                  use air-conditioners.

A. have                  B. have to                          C. needn't                         D. need

32.  Plant more trees in the schoolyard because they will provide shade and             the atmosphere fresher.

A. do                     B. make                             C. have                              D. use

33.  Our dream house will use only solar energy so that we can make the                 clean and green.

A. nature               B. environment                 C. kitchen                         D. home

34.  Many products are now helping you                    your energy bills.

A. reduce              B. reuse                             C. recycle                          D. cut down

35.  It takes a lot of energy to keep food cool, so don't                       the fridge door open or putting hot things inside.

A. make                 B. have                              C. leave                             D. stop

36.  Future houses will have hi-tech                rooms for all of the family members.

A. read                  B. to read                          C. reading                         D. to reading

37.  Our houses will use the sun or the wind               electricity.

A. to have              B. to do                             C. to make                         D. to give