With the fact I draw for a living, we can just easily mark out D, because this obviously not watercolors. It is not B, because wax is a thicker color, and can not make a light faded grey/black. We are now left with both A, and C. I would most likely go with C, because this item is still being drawn. If using clay, it leaves a print after the tracing that would all be grey, or colored depending on clay color. Graphite pencils is the only reasonable option here, because its a simple drawing of flowers, with no color.
Here is a dog to brighten your day!
DOG:
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