5.1 b) Sorry, I don’t smoke.
5.2 a) I am afraid he is attending a meeting at the moment.
5.3 b) do you go to London?
5.4 a) I think you would not
5.5 b) been there before?
6.1 a) have
6.2 h) been
6.3 d) has
6.4 i) being
6.5 b) to have
6.6 f) be
6.7 g) to be
6.8 c) having