Radio waves are visible. Radio waves have a high frequency. Radio waves spread in all directions. Radio waves are created by the animal.
I gave my students this multiple choice question: Collars that emit radio waves are sometimes placed on animals to find their location. Which is the best reason for using radio waves as a method of tracking the animals?

Only one answer is correct among these 4 choices:
- Radio waves are visible.
- Radio waves have a high frequency.
- Radio waves spread in all directions.
- Radio waves are created by the animal.

Could you tell me which one is correct?

Radio waves spread in all directions.