Line vs. Shape

I think that a, b, and c are lines, and all four images are shapes as well. I think that image d is the only one that cannot be considered a line because of how complicated it is. The first three images can all be done with one stroke of a pen or marker. Granted, the marker would have to be thick, but it is possible. I consider these all shapes because they have some sort of form to them, there are dimensions to them.