Ex. 5.
a. I was tired because I had been doing physical exercises all morning.
b. He put on a lot of weight because he had been eating too much bread.
c. They failed the test because they had not been studying hard.
d. This building had been in use for years before they pulled it down.
e. They had been waiting there for a few minutes when the coach arrived.
f. When I arrived at the theatre the play already begun.
g. My father had been working in the army for thirty years before he retired.
