Answer: I think I separated the sentences correctly.
If I separated them correctly then the correct answer would be the second one.
Step-by-step explanation:
He wrote many scholarly essays about a variety of topics the teacher explained.
He wrote many scholarly essays about a variety of topics,
“He wrote many scholarly essays about a variety of topics,”
“He wrote many scholarly essays about a variety of topics”.
“He wrote many scholarly essays about a variety of topics”