Ex.1
1. C (are)
2. B (is)
3. A (am)
4. C (are)
Ex.2
1. are taking
2. are visiting
3. is going
4. am swimming
Ex.3
1. Patrick isn't playing basketball.
2. Mary isn't doing her homework.
3. The girls aren't reading.
4. Mrs Reed isn't visiting the market.
5. My dog isn't sleeping.