A man who was severely bitten by a dog as a child is beginning cognitive restructuring therapy to treat his posttraumatic stress disorder (PTSD). He identifies walking down the sidewalk past a person with their dog on a leash as a highly distressing situation, rating his fear during such an encounter as 80/100. He states that he strongly believes any dog is likely to escape its leash and attack him. The next step in cognitive restructuring would be for him to:

a) Reinforce the irrational belief
b) Avoid situations involving dogs
c) Challenge the irrational belief
d) Increase avoidance behaviors