What Is the Collective Purpose of Nasal Hair, Mucus Secretions

What is the collective purpose of nasal hair, mucus secretions in the naspopharyngeal tract, phagocytic cells in the throat, bronchial lysozyme, sneezing, and coughing?

A) To keep organisms from entering the lower respiratory tract and causing infection.
B) To keep normal flora in the oropharynx from entering the eustachian tube causing infection.
C) To keep normal flora in the oropharynx from causing infection.
D) To maintain a sterile environment in the oropharynx.