A middle-aged psychology professor has been tipped off by one of his students that cell phones are going off in the classroom. The professor does not recall hearing a cell phone go off anytime in the last few days in class. What is the most likely explanation?

a. The student who tipped off the professor about the cell phones really made up this false story in order to play a joke on the professor.
b. The students in class have downloaded a high-pitched ring tone that the professor cannot hear because of a loss of hair cells.
c. The students in class have downloaded a low-pitched ring tone that the professor cannot hear because of a loss of hair cells.
d. The professor has a severe conductive hearing loss.

B