I believe that these are the correct answers:
Why would an artist want to vary the line weight in a drawing?
a. to control the color of the line
This is because if you have a heavy pencil weight, the color is straight up black, but when the lines are thin, they will be gray.
Jacob drew the outer edge of a rabbit's ears. What did he draw?
b. form or c. outline
The outer edge of a shape is the outline. The form of something is the pre-drawing.
Melanie drew a silhouette of a house. What did she draw?
c. outline
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