Consider the following statements about ultrasonic waves.
1. They can destroy insects.
2. They can clean clothes by removing dust.
3. They can be used to treat diseases.
4. They can control automatic doors.
Of the above statements.

A. 1 and 2 are correct

B. 3 and 4 are correct

C. 1, 2 and 3 are correct

D. All are correct

Answer: Option D