Read the excerpt from "On Becoming an Inventor" by Dean Kamen. My next challenge was that I wanted to make things out of metal, so I became interested in how to use a lathe, a milling machine, and so on. I went to buy this new equipment I thought I'd need and met a man who had a machine shop of his own who was about to retire and move to Florida. He allowed me to visit him after school and on weekends to observe how he used all his tools. I was hooked. When he retired I bought not only all his big equipment but all his little toolboxes as well--they were treasures!

Which statement from the excerpt expresses an opinion rather than a fact?

a man who had a machine shop of his own . . .
He allowed me to visit him after school and on weekends . . .
When he retired I bought not only all his big equipment . . .
his little tool boxes as well—they were treasures