2-C. He started cooking for his family regularly, and then later for his friends at college.He started cooking for his family regularly, and then later for his friends at college.
3-C. Then, by watering them regularly, you can ensure that they get enough moisture to grow.Then, by watering them regularly, you can ensure that they get enough moisture to grow.
4-C. People who regularly do not get enough sleep may be at risk of dying earlier than those who usually sleep well.People who regularly do not get enough sleep may be at risk of dying earlier than those who usually sleep well.