1. Radu "is" good at physics.
2. Sara and John "are" very good friends.
3. I "was" at school yesterday. I didn't feel well.
4. My brothers "are" at the dentist now.
5. Paul "was" at home yesterday. He went to the seaside.
6. Your girls "are" very hungry. They didn't eat for lunch.
7. Sam says he "is not" afraid of dogs. He loves dogs.
8. My sister "was" 6 years old two years ago. She is 8 now.
9. Tom "is not" a vet. He teaches English and German at the University.
10. My mom "is" at the doctor now. You should call her later.
Hope I helped ;)