After using the phrase "It is/was..." for emphasis in each sentence, we have the following:
1. It was Mr. David who saw that I could also take part in the contest.
2. It wasn't I who invited them.
3. It was at that moment that I began to think about everything.
4. It is his attitude towards other people that really annoys me.
5. It wasn't I who decided to postpone the match.
6. It wasn't the candidates who started the trouble.
7. It is the computer that gives me a headache.
8. It was on Monday that my uncle came.
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