Take a look at the sentence again:
The problem occurs between RaShaunda and because. Anthony kept flirting with RaShaunda is a main clause, so it can stand alone as a complete sentence. Because his behavior was keeping Shenicka from understanding the lecture, Shenicka whacked him ... begins the next complete sentence. Since these two parts have only blank space between them, they make a fused sentence, a major sentence error.
To fix the problem, you could put a period after RaShaunda and then capitalize the B for because.