Answer:
B. Assertion.
Explanation:
In the given passage, the speaker remembers how he was greatly impressed by the quips he read in a book. The quip he found funny and effective was by Robert Benchley, who jokes about the two types of people in the world.
Looking at the quip, we the readers are also quite expectant of something that shows a demarcation of these two groups of people. But all this is removed when Benchley states "<em>those who divide the world into two kinds of people and those who don't</em>". This is comic, and makes the speaker as well as us, laugh at it though the result was quite unexpected.
So, in using the last line "<em>Humor is based on the unexpected</em>" as a thesis statement and a topic sentence, the speaker asserts that things like that are what humors people more than the real, common jokes. The assertion that the unexpected is what makes it funny makes the whole thesis statement an effective one for the paper.
