Question

Which sentence contains correct capitalization? What? who is required to attend the meeting this afternoon? What? Who is required to attend the meeting this afternoon? What, Who is required to attend the meeting this afternoon?

Answer 1

What? Who is required to attend the meeting this afternoon?

Answer 2

Answer:

B: What? Who is required to attend the meeting this afternoon?

Explanation:

 The sentence in option B contains correct capitalization because What? is a separate and complete expression, asking for some confirmation. The next sentence begins with correct capitalization in Who, differently  from sentence A. The sentence C is wrong because it doesn't have question mark, capitalization is used after a comma.