The key answer of exercise 3

a)

1. The amazing thing is that the tiger ran off,
2. Wow, there's no way I'd do that!
3. You're the one who's always telling me to stop.
4. That is so wrong!
5. That's totally outrageous!
6. I do think they should do something about it.
7. That is a good idea.
8. How on earth did he catch it?
9. That's such an amazing thing!
10. Absolutely incredible!

b)

1. So is followed by adjective / adverb, such is followed by (a / an) + (adjective) + noun.
2. Do is not normally used with the present simple affirmative. It is used here to emphasise an opinion.
3. Any adverb that can be used with an ungradable / extreme adjective, e.g. really, completely, just, quite. Very can't be used.
4. It adds the one who's to emphasise the person.
5. on earth, e.g. What / Why / Where / Who on earth …?