Answer:
Option C: an outline of a pine tree
Explanation:
Artists usually use two main types of shapes when drawing. One is geometric shape and the other is bimorphic shape.
A geometric shape simply refers to common regular and precise shapes like triangles, rectangles, squares which are commonly found in man made objects. Whereas, a bimorphic shape is one that is basically rounded or irregular and depicts natural things or living organisms.
Now, from the question, the only thing there that refers to a natural occurring object is "an outline of a pine tree".
Thus, it is a bimorphic shape.