Q: 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").
Fact1: a cavern is formed by carbonic acid in groundwater seeping through rock and dissolving limestone, Fact2: Underground caves and caverns pose an exciting adventure to many., Question: What can be formed by carbonic acid in groundwater seeping through rock and dissolving limestone? (A) water (B) swamp vegetation (C) Calcium carbonate (D) sunlight (E) contamination (F) loose soil (G) underground caves (H) arsenic
A:
G