Fact 1: Sound can be used for communication by animals. Fact 2: Sound vibrations have different frequencies. Given the two facts above, what can be used for communication by animals?
Pick from:
[I] electricity.
[II] energy.
[III] Telephones..
[IV] Vibrations..
[V] Stuffed animals..
[VI] messengers.
[VII] courtship.
[VIII] Cellular communication..
Answer:
[IV]