Instructions: In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").
Input: Fact1: Roundworms make up the phylum Nematoda., Fact2: Also, nematoda and rotifera are important groups contributing to soils., Question: _ contribute to soils. (A) Sediment (B) Aphids (C) cacti (D) Roundworms (E) Exfoliation (F) Amphibians (G) Ringworms (H) rainfall
Output:
D