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 delta is formed by deposition of sediment at the mouth of a river by water fanning out, Fact2: Deltas and estuaries are important habitats., Question: what is formed by deposition of sediment at the mouth of a river? (A) A solid geometric shape (B) clouds (C) h2o (D) important habitats (E) dams (F) patch reefs (G) swamp vegetation (H) at or near the margins
D