Rainwater picks up carbon dioxide from the air and as it percolates through the soil, which turns into a weak acid. This slowly dissolves out the limestone along the joints, bedding planes and fractures, some of which become enlarged enough to form caves.
A. The wave form moves forward, but the water particles do not advance appreciably.
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It's the epidermis, because it is the outermost layer of our skin, it creates a waterproof barrier and creates skin color pigmentation.
Answer:
I think the answer is A) biological species concept