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: All chemical reactions require activation energy to get started., Fact2: Catalysts lower the activation energy., Question: In what way does a catalyst help in chemical reactions? (A) Generating heat (B) lowered energy cost (C) metabolic reaction (D) heating liquids (E) by making heat (F) adding heat (G) increases a body's strength (H) preventing heat transfer
B