1. aren't – are not
ex: - Why aren’t you answering your phone?

2. can't – can not
ex: - I can't find my glasses anywhere.

3. didn't - did not
ex: - They didn't tell me the meeting was cancelled.

4. hasn't - has not
ex: - He hasn't been in touch for over a month.

5. mustn't - must not
ex: - You mustn't be late for work