This is largely an opinion question, asking for your subjective view of the art itself, meaning that your teacher is seeking your own personal interpretation of the artwork.
However, if I were to be asked, I would look most immediately at the black-clad figure behind the painting's most prominent character. We don't really know why he's there, but he seems to be the reason that "The Scream" is, in fact, screaming.
In addition, one might want to analyze the use of color in this work -- Why so much red? Is the artist symbolizing rage, madness, or something else? And what about that wave of blue that seems to be a river beneath the bridge itself? What does it really mean, besides just being a body of water? Black overtones carry the paintings sinister or darker theme, while the character's facial features, impressionistic though they may be, indicate extreme disturbance.
Why is this character on what seems to be a bridge? What do bridges symbolize? Passages or transitions from one place (or thing) to another. The best way for you to analyze this painting is to begin by asking the types of questions you see above. Best of luck.