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").

[EX Q]: Fact1: when a metal rusts , that metal becomes orange on the surface, Fact2: Iron rusts in the presence of oxygen and water., Question: Exposure to oxygen and water can cause iron to  (A) decrease strength (B) melt (C) uncontrollable burning (D) thermal expansion (E) turn orange on the surface (F) vibrate (G) Extremes of temperature (H) levitate
[EX A]: E

[EX Q]: Fact1: some animals' fur grows thicker for staying warm in the winter, Fact2: During winter, their hollow fur absorbs much heat as they sun themselves., Question: hollow fur keeps animals what (A) fats (B) camouflaged (C) safe (D) warm (E) cooled (F) liquid (G) live (H) from drowning
[EX A]: D

[EX Q]: Fact1: Cnidarians are invertebrates such as jellyfish and corals., Fact2: An invertebrate is an animal that has no spine, or backbone., Question: What don't cnidarians such as jellyfish and corals have? (A) a hosta (B) backbones (C) space between (D) a marine habitat (E) flagella (F) sea anemones (G) cells (H) cartilage
[EX A]:
B