What are you doing?
---- I'm watching TV.(肯定) / I'm not watching TV.(否定)
What is he(she) doing
--- He(She) is reading a book.（肯定） / He(She) is reading a book.(否定) What are you doing?
---- I'm watching TV.(肯定) / I'm not watching TV.(否定)
What is he(she) doing
--- He(She) is reading a book.（肯定） / He(She) is reading a book.(否定)