Question to you: _ contribute to soils.\nOptions:\n- (A) Sediment\n- (B) Aphids\n- (C) cacti\n- (D) Roundworms\n- (E) Exfoliation\n- (F) Amphibians\n- (G) Ringworms\n- (H) rainfall.
Let's reason step-by-step:
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Roundworms make up the phylum Nematoda. Also, nematoda and rotifera are important groups contributing to soils. Roundworms contribute to soils. Final answer: (D).
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