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: poisonous darts are used for defense by sea anemones, Fact2: Protection at the gateway is the best defense., Question: What are used as protection by sea anemones? (A) lamphreys (B) poisonous darts (C) tubular organ (D) feed on dead protists (E) coelenterates (F) islets of Langerhans (G) related organisms (H) moisturize their skin
[EX A]: B

[EX Q]: Fact1: damming a river can cause a lake to form, Fact2: Beavers know how to cut wood and build dams., Question: How do beavers change waterways? (A) They warm up the water (B) marshes, bogs, and swamps (C) They soil the water (D) Earth's axis of rotation is tilted (E) several different ways (F) They make structures that split the water (G) Genetic diversity is increased (H) By tearing down dams
[EX A]:
F