Detailed Instructions: 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").
Problem:Fact1: increasing heat causes thermal expansion, Fact2: Liquid propane is used to heat hot air balloons., Question: How is liquid propane used in hot air ballooning? (A) lowered energy cost (B) The area was once underwater (C) to expand the balloon (D) energy of moving objects (E) activation energy (F) hydrogen and oxygen (G) It remains dormant (H) to move people
Solution:
C