For safe listening, limit listening to a portable music player ...

[serike]

For safe listening, limit listening to a portable music player with earphones or earbuds at ____ percent of its potential volume to ____ hour(s) a day.
 A) 30; three
  B) 50; two
  C) 60; one
  D) 70; two
  E) 80; three

Question 2

What is the lowest frequency that the human ear can consciously detect?
 A) 50 hertz
  B) 500 hertz
  C) 4,000 hertz
  D) 10,000 hertz
  E) 20,000 hertz

[BAOCHAU2803]

Answer to Question 1

C

Answer to Question 2

A