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 taki ng 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.