text: The correct choice is "C: 1,000 Hz."  If you go to a piano keyboard, the A below "middle C" is at 440 Hz.  Every time you jump up one octave to the next A, you double your frequency, so the A above middle C is 880 Hz, and the one above that is 1760 Hz.  Since 1000 Hz falls between those two (obviously audible) notes, it must be audible itself.\n\nIn fact, every half-step (walking up the keyboard, both black and white keys) is about 6% higher in frequency.  As it turns out, the B and C above middle C are at about 987.8 and 1046.5 Hz, respectively, so your 1000 Hz tone is between them.