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 solution is formed by one substance being dissolved in another substance, Fact2: Another dissolved substance in ocean water is a type of rock called limestone ., Question: A solution is formed when limestone is dissolved in what? (A) old caves (B) habitats (C) body water (D) rainfall (E) calcite (F) sandy shores (G) evaporation (H) ocean water
H