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: Biodiversity increases the productivity and stability of ecosystems., Fact2: An ecosystem includes the organisms and their habitat., Question: what does biodiversity increase the productivity and stability of? (A) density (B) the looseness of soil (C) water vapor (D) the environment (E) h2o (F) swamp vegetation (G) biological diversity (H) organisms and their habitat
[EX A]: H

[EX Q]: Fact1: Feathers help birds fly and provide insulation., Fact2: Some birds are flightless birds., Question: Why do the flightless have feathers? (A) layers of fat (B) Sublimation (C) it needs them (D) warm-blooded (E) Air conditioning (F) Radiation (G) Insulation (H) protect them
[EX A]: G

[EX Q]: Fact1: coal is used to produce electricity by burning in coal-fire power stations, Fact2: Most of the electricity in the United States is produced by burning coal., Question: What kind of power stations create most of the electricity in the United States? (A) coal (B) making (C) motors (D) energy (E) cars (F) made (G) heat (H) two
[EX A]:
A