In Spanish, the subject is not necessary because the verb is conjugated duly with the subject. Therefore !Habla! can be a possible answer.
"¡Habla!" sounds like the imperative, like you are talking to someone and telling them to speak. If you said only that to a Spanish speaker I'm sure they would assume that is the case. You need the pronoun when there's such a big risk of ambiguity.
True -- But if you want to be sure the reader knows it is a "he" speaking you need the El. Habla can be he/she/it speaks.
This appeared under the occupations section and seems entirely irrelevant to the subject.