The lights of the bikes look like fireflies above the desert sand, since it is dark and all you see are the lights. the rest of the vehicle bodies are essentially invisible, and the lights appear to be at a height above the sand, and not directly on the sand.
Well, vegetarianism is most likely not a word. I used to be a vegetarian, so my answer would be D., because anything with the suffix "ism" is usually a belief.
