Since the identity of the man was not known and was being referred to for the first time, I would use the indefinite article "a".Let’s suppose there are an interviewer and an interviewee.
Each of them is looking at a picture while holding it in his/her hands.
The two pictures are exactly the same, and in the picture(s),
there are five people doing different things and a person
inwearing a cap is singing.
The interviewee has to describe what each person in the picture is doing.
How should I start
Student or Learner