Every Year During the Finals Week in December,Judy Would Come

Every year during the finals week in December,Judy would come down with a severe cold.It was the only cold she would get each year.What is the most likely explanation for this pattern of colds?

A) Cold viruses are most prevalent in December.
B) The stress of final exams left Judy more susceptible to colds.
C) Judy's roommate caught a cold every December and gave it to Judy.
D) It is just a random pattern of colds.