Which has a higher frequency — ultrasonic sound or infrasonic sound?

Complete the following sentences —

(a) An average person can hear sounds of frequencies in the range ………. to ……….

(b) Ultrasound is of frequency ……….

(c) Infrasonic sound is of frequency ……….

(d) Bats can produce and hear ………. sound.

(e) Elephants produce ………. sound.

What is ultrasound?

State the approximate speed of ultrasound in air.