You will be given a definition of a task first, then some input of the task.
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: a breathing mask is used for keeping harmful particles from entering the respiratory system, Fact2: When inhaled, the particles lodge in the respiratory system, causing or aggravating health problems., Question: a breathing mask keeps what from being inhaled and causing health problems? (A) cigarettes (B) harmful particles (C) chemical changes (D) influenza (E) oxygen particles (F) hydrogen and oxygen (G) air particles (H) atmosphere particles
Output:
B