Which of the following condition would decrease the ability of a person to hear a sound?

These are some conditions that can possibly decrease the ability of person to hear a sound:
1. Blockage of the ear canal -  ear wax is naturally produced by our ear canal which serves as self- protection. It also block sounds if the ear canal is not well cleaned. 
2. Foreign bodies in the ear canal - foreign bodies such as beads, left residue of cotton, peas or even small insects like bugs, bees, and spiders. 
3. Infected Eardrum - eardrum catches sound waves that passes through the ear canal. If the eardrum is damage, it may lessen its ability to catch sound effectively.

The answer is 12, for the points