The subordinate clause in the sentence is option D: whereas Gordon preferred to play baseball.
A subordinaye clause is one which do not form a complete sentence, it depends on the other part of the sentence to have a total sense.
A subordinate clause, also known as a dependent clause, will begin with a subordinate conjunction or a relative pronoun and will contain both a subject and a verb.
In this case the word whereas indicates that it is a subordinate clause since it is a subordinate conjunctions.
Gulliver calls up Descartes and Gassendi to school Aristotle in their systems. Aristotle freely admits his own errors. Still, he says that new theories of nature go in and out of fashion and even those that purport to be grounded in timeless mathematic principles will vary from age to age. Gulliver also calls up the Roman emperors.