Answer the following question: Fact 1: Hearing is used for sensing sound by animals. Fact 2: Sound waves enter the ear, and are then amplified. Given the two facts above, what uses ears to hear?

(I). Stereos; (II). humans; (III). TVs; (IV). Animals; (V). Mammal; (VI). organisms; (VII). pigeons; (VIII). Plants;
Answer:
(IV).