Well, since we know an antonym is the opposite, and patronize means to treat someone kindly, we can choose C. scornful. :)
If I had to take a guess I believe he means that he is a very smart intelligent history teacher. He is familiar to the topic of history and knows enough to be a teacher, and a very good one at that. I hope this answer helped and I'm sorry if it didn't.
The best method a writer can use to present an argument is order of outstanding feature. The outstanding<span> or marked property will attract all the attention and that is the argument. </span>