Consider the following statements.
1. The heart vibrates at infrasonic.
2. The speed of sound is more in gas than in liquid and solid.
3. Mach number is used to describe the speed of sound.
4. Ultrasonic sound has frequency more than 20,000 Hz.
Of these statements.

A. 1, 2 and 3 are correct

B. 2, 3 and 4 are correct

C. 1, 3 and 4 are correct

D. 1, 2 and 4 are correct

Answer: Option C