What do you think about (him,his) being chosen as class president. Both seem correct to me. Is it his? If not, what makes it work here?

Would it be his?

In this case, the correct pronoun to use is "his." Let me explain why.

When referring to someone as the subject of a sentence (the one doing the action), we use the pronoun "he." For example, "He is chosen as class president."

When referring to someone as the object of a sentence (the one receiving the action), we use the pronoun "him." For example, "I saw him being chosen as class president."

However, in your question, you are using the possessive form of the pronoun, which is used to show ownership. Here, you are asking about the class president's selection. So, we use the possessive pronoun "his." For example, "What do you think about his being chosen as class president?"

To further clarify:
- "Him" is used as an object pronoun (e.g. I saw him).
- "He" is used as a subject pronoun (e.g. He was chosen).
- "His" is used as a possessive pronoun (e.g. His accomplishment).

Therefore, in this particular case, the correct pronoun to use is "his" because it functions as a possessive pronoun indicating the ownership of the class president's selection.

him. "His" requires some possession, e.g., his choice.

NO. See my previous answer.