Answer:
Cleaning.
Explanation:
Ultrasound are the high sound waves that has the frequency above than 20kHz. The ultrsonic sound can be detected by animals like bats and has medical importance as well.
The cleaning of the medical instruments and machines are done by ultrasonic cleaners. These cleaners uses the ultrasonic waves to clean the dirt and needs a proper solvent medium for cleaning. The cavitation bubbles are produced that are used for cleaning.
Thus, the correct answer is cleaning.
<span>A is the correct answer. The developmental norms are stages at which humans typically develop the ability to successfully complete an activity without aid, for example, being able to walk. When people have reached the age of the norm and cannot complete the activity, there may be cause for concern.</span>
