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Which one of the following statements is incorrect?

(i) A sound of frequency 1,08,000 hertz is an infrasonic sound

(ii) If an object vibrates at the rate of 120 vibrations per second then it will produce sound audible to us.

(iii) Ultrasonic sound can be used to study the growth of foetus inside the mother's womb.

(iv) Human being can produce ultrasonic sound but cannot hear.

(v) A sound can never have frequency less than 20 hertz.

A) i, ii and iv

B) ii, iii, iv

C) i, iv and v

D) ii, iv and v

E) None of these