which excerpt from "on becoming an inventor" by dean kamen expresses a fact rather than an opinion?

a. kamen believes it may change the way people move around in crowded cities . .
b. i took the pictures, though somewhat reluctantly. i didn't like the blood.
c. at college i was struck by how smart the teachers were—in electronics, in physics, and in mathematics.
d. i didn't officially graduate from worcester polytechnic institute until years later when i was awarded their honorary ph. d.