Based on the sentence, which transition best indicates a chronological sequence? My face instantly flushed red, and I knew that I had to formulate a plan.

First, I needed to act as if the ridicule didn't bother me at all.

Explanation:

quite an interesting way to teach topic sentences, because the answer to this question is the best definition of a topic sentence that one can present, it is as if answering the questions taught you how to do it, this is some real teaching, it is terribly well-done.

the topic sentence in this paragraph is:

topic sentences writers stay on track and keep a paragraph from becoming an aimless collection of sentences about an idea.

which incidentally tells you what a topic sentence should be.

we need more information in order to answer.