Answer the following question: Fact 1: Roundworms make up the phylum Nematoda. Fact 2: Also, nematoda and rotifera are important groups contributing to soils. Given the two facts above, what contributes to soils?

Choose your answer from: 1). roundworms. 2). humans. 3). rainfall. 4). cacti. 5). bacteria. 6). weathering. 7). viruses. 8). Most plants.
Answer:
1).