When You Were in High School,your Friends Had "Mosquito" Ring

When you were in high school,your friends had "mosquito" ring tones on your cell phones,which were very high-pitched (17kHz) tones.What did your 45-year-old teachers think of it?

A) Some of the teachers thought that there was an invasion of mosquitoes at your school.
B) Most the time the ring tones were very quiet and the teachers seemed to like them.
C) They found the high-pitched noise to be very irritating.
D) Most never heard it.