1.coal is more expensive and more polluting than natural gas
2.we are looking for a cheap and clean and effective sourced of energy
3.will fossil fuels ne replaced by solar and wind within 20 years
4.i have visited yaly hidroelectric power plant before
5.... was built in niagara falls in 1879
6.you should swich off electrical appliances ...
7.despite the polution of coal,it's still the largest sources of energy worldwide
I
1b
2d
3a
4c
5c
6
II
1a
2c
3b
