Select the correct answer 1. Instruments that produce sound are called sources of light.

2. Music has no ability to heal the mental stress.

3. A medium is necessary for sound travel.

4. We hear sounds of frequencies below 20 Hz. O First answer O Second answer O Third answer O Forth answer

Explanation:

Option 3rd is correct..

C or 3

Explanation:

A: no they are called sources of sound. A is incorrect.

B: It does. Many people attest to this. But this is not a property of physics.

C: A media is required is the correct answer.

D: Dogs might. In general we don't.

I would pick C

a coal burning power plant

the closer the planet is to the sun, the larger the gravity