Question

explain how bats use ultrasound to catch the prey

Answer 1

because they have more more more than a frequency 20000 Hertz

Answer 2

Bats emit ultrasonic waves from their mouth. When these touch the prey, the waves get reflected back to the bat. the bat detects these waves and his brain estimates the distance and direction of the prey by the time taken, the loudness of the sound and the direction of the sound.