Yes, because a simile uses 'like' or 'as' and as of course the sentence contains "as".
Answer: A. George Stephenson was joined by other inventors to enhance the design of locomotives.
Explanation: I got it right on Edmentum.
The underlined word <em>unique </em>is used as C. predicate adjective in the sentence.
A predicate adjective is the adjective following a copulating/linking verb.
The linking verb here is <em>is, </em>and the predicate adjective is therefore the adjective following it, which is <em>unique. </em>