19.Students are more aware of protecting the environment. Teachers teach environmental issues 
at school.
=> ............................................................................................................
( Combine each pair sentences to make a conditional sentence Type 1)
20.There are so many billboards in our city. People can’t not see clearly.
=> ……………………………………………………………………………………………
    ( Combine each pair sentences to make a conditional sentence Type 2)
21. We turn on the lights all day. We have to pay a lot of money for electricity a month.
=>………………………………………………………………………………………….
( Combine each pair sentences to make a conditional sentence Type 2)
22.People throw litter on the ground. Many animal eat litter and become sick. ( because) 
=>......................................................................................................................................
23. He can’t see the stars at night.There is too much light pollution. ( due to)
=>...................................................................................................................................................
24- My father finished repairing our roof, then he went to help our neighbors after the storm last 
night.
Before my father …………………………………………………………………………….
25. The oil spilled .Many seabirds were dead. ( because of)
=>...................................................................................................................................................
26.We have decided to cancel our picnic. It’s forecast to rain tommorrow. ( since or because) 
=>............................................................................................................................................
27. Acid rain is dangerous. Trees’ leaves are damaged. ( because of)
=>...........................................................................................................................................
28.The area is uninhabitable. The Chernobyl nuclear accident happened. ( Make)
=>...........................................................................................................................................
29.Noise pollution happens. There is a change in animals’ living pattern. ( causes) 
=>.........................................................................................................................................
30. They quickly send food and medical supplies to the victims of the typhoon
 Food and medical ………………………………………………………………………
31. I am poor so I can’t buy this expensive car.
=>..........................................................................................................................................
( Combine each pair sentences to make a conditional sentence Type 2)
32. They are going to service our car by a mechanic tomorrow morning.
=>Our car is going.................................................................................................................
33.I am not you, but I think you should recycle these plastic carrier bags. 
=>If........................................................................................................................................
(a conditional sentence Type 2