D) Yo soy el mesero
This is the answer is correct because when one uses Yo they have to use soy because they are talking about their selves. B and C would not be the answer because Ella is used for a girl not for a boy and the picture clearly shows a boy so the subject pronoun one should use is el. Also when one uses Ella they have to use es following it. So obviously A and B does not make any sense.