The line from the excerpt that expresses fact rather than opinion is:
Let's understand what fact is all about.
Fact actually refers to something that is well known and proven to be true. Facts are used to backup evidences.
From the excerpt, the information that actually provides us with fact is one that tells us about what Dean did. For Dean to have gotten alot of patents in his lifetime, that means he started somewhere. Definitely, he stocked the basement laboratory with machinery which helped him in his work.
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