Every mobile phone has a ringtone (铃声). It tells you that someone is calling you. Now, there 1 a ringtone called " mosquito tone (蚊子铃声)".

Mosquito tone has a special 2 . Only children and teenagers can hear it. Using it, students can receive calls and text messages in class 3 the teacher will not realize what is happening. However, it also has a bad influence on their study if students use it in class.

"Not all the students are 4 in mosquito tone." Jerry Jones, a high school student of 17, says, "Using mosquito tone too often is bad for our hearing. I may use it for 5 , but not in class."