Где обычно проходят королевские шествия в лондоне

b: then where have you been? (present perfect)

a: oh, nowhere. i wanted (past simple) to go to america two years ago,but now i don't want to go there.

b: why?

a: i understood (past simple) that my wish is impossible, so i abandoned(past simple) that idea. 

и 2-я

b: have you heard some interesting news? (present perfect)

a: no.

b: i heard (past simple) that brian flunked (past simple) his exam last week. 

a: why did (past simple)he flunk the exam?

b: he lost (past simple)his homework, so he didn't repeat a topic.(past simple)

1.a garbage is not only ugly, bute dangerous because it causes an air pollution.

2. cars are an important part of a life for most people. but cars also cause a pollution and release fume.

3. in canada people don't realise that they throw out 10,000 tons of a waste.

4. over 14 billion pounds of a waste per year is throw out to sea and it kills millions of sea animals.

5. if we want to breathe  a healthy air we have to think about what we do.

6. because of our lack of a knowledge there is now a huge hole over an antractic.

7.a water is a vital element of a life.