1. In some cities, rubbish ................ to produce electricity.

burn

burns

is burnt

is burring

2. Water ................... to turn it into steam.

heat

is heated

are heated

is heating

3. She often ............. at the weekend.

is working

works

was working

work

4. We .............. different types of energy today.

are used

use

using

to use

5. We ........... tennis every Friday

play

are playing

played

are played

6. She frequently ........... the Pyramids

is visiting

has visited

visits

is visited