1, C – pollution
2, D – were
3, C – bought
4, A – air pollution
5, C – had
6, A – make
7, C – because of
8, A – think of
9, C – surface
10, B – weather
11, B – could -> can
12, A – because of -> because
13, Minh is tired so he doesn’t go to work.
14, The children like going swimming because of the fine weather.
15, If you don’t water these trees, they will die.
