_ 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
Please answer and provide answer explanation.
(D)
Roundworms make up the phylum Nematoda.

Also, nematoda and rotifera are important groups contributing to soils.

Roundworms contribute to soils.

.

Thus, the answer is (D)