Answer:
From behind
Explanation:
This is because, a silhouette can only be formed by an object if the light is coming from behind the object. For example, if a shadow of an object is to be formed, the light shone on the object must be coming from behind the object.
Similarly, for a complete silhouette of the person's face, the light must be coming from behind the person's face for it to form a shadow and then a silhouette.
So the light must come from behind.