Ernie's new cat slept on Ernie's bed all day Monday. When Ernie got in bed on Monday night, he started sneezing, even though he had not had this problem on previous nights. He sneezed all night, and in the morning he thought about what might have changed, and then he washed his sheets. Tuesday evening, Ernie did not sneeze once in bed. Based on the given information, what is a reasonable conclusion to draw?

a)	Ernie's cat is sick.
b)	Ernie is allergic to cats.
c)	Ernie suffers from seasonal allergies.
d)	Ernie is allergic to his laundry detergent.