I believe the pronoun "what" is already properly placed.
A. he talked about the conflicts of slavery, how it shouldn’t be spread to the north, and how it caused the clivil war
Answer:
The phrase between brackets is a <em><u>gerund phrase</u></em>.
Explanation:
A gerund is a verb form that can function as a noun in a sentence. It is the '-ing' form of the verb that identifies as a noun.
A gerund phrase is a group of words that starts with a gerund and contains modifiers, nouns, or pronouns that acts as a direct object or can act as the subject in the sentence.
In the given sentence, the words in the brackets is a gerund phrase. It starts with the '-ing' form of the verb.