Detailed 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").
Q: Fact1: bacteria in soil convert atmospheric nitrogen into a form usable by plants, Fact2: Rhizobial bacteria convert atmospheric nitrogen into nitrate fertilizers in a form usable by plants., Question: What does rhizobial bacteria do for plants? (A) Converts oxygen (B) nutrients (C) Converts h2o (D) Converts nitrogen (E) Regrows it (F) hydrate their cells (G) Converts methane (H) competing for resources
A:
D