用所给词的适当形式填空。
1. Bill Gates became ________ (interest) in software when he was only 13.
2. Bill Gates is the man who is taking the ________ (person) computer into everyone's home.
3. Mrs. Wang is very nice. She is ________ (friend) to us every student.
4. Grace is very sure of ________ (she).
5. My father plans ________ (retire) at the age of 50.