Given the task definition and input, reply with output. 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: sand dunes are formed by the wind transporting and depositing sand, Fact2: Winds are caused by pressure differences., Question: Sand dunes can be formed by (A) air mass over Earth's surface (B) movements in the earth's crust (C) The bending of a ray of light (D) Movement of an air mass (E) pressure differences. (F) Physical weathering (G) looseness of dirt or compost (H) remains of prehistoric life
E