Fish poop.
Tropical white beaches get their pearly white color from the excrement of fish far off of the coast which eat coral and other things that reside on the ocean floor. When they eat they swallow some sand into their mouths as well, and process it with the food they just ate. Their stomachs can't really digest the sand, tiny minute rocks essentially, and thus turn their color white. Or the rock forming the sand can be naturally pigmented a whitish tone as well.
I would say B) <span>The shoot is positively phototropic and negatively gravitropic; the root is positively gravitropic and negatively phototropic.
This is because the shoot of the plant is attracted towards the sun, as the chloroplasts in the leaves need sunlight to make food. As well, the roots are attracted downward to absorb more water and minerals from the sun.
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