Why is the first comma correct in the following sentence taken from the "Rice for Thanksgiving" article?

> It seemed like everyone expected me to fit inside that box, and I sometimes worried that I wasn't Asian enough, like I was pretending.


A. The comma is used to set off ideas that follow a complete sentence.


B. The comma is used to separate two or more descriptive words that describe the same noun and can be connected with the word "and."


C. The comma is used with a coordinating conjunction to connect two complete sentences.


D. The comma is used after an introductory word attached to the beginning of a complete sentence.