Which frequency range includes all ultrasonic waves?

PYQ UPPSC LT Grade (Assistant Teacher) 2025· Modified — slightly modified from the official paper; see the solution

1. A.

   More than 50,000 Hz

2. B.

   More than 20,000 Hz

3. C.

   20 Hz to 20,000 Hz

4. D.

   Less than 20 Hz

Attempted by 101 students.