premise: a bat is a kind of animal sent2: bats find their prey by sensing echos sent3: echo is when sound reflects off of a surface sent4: a sound must first be emitted before it can reflect off of a surface sent5: hearing is used for sensing sounds by animals sent6: echolocation is when some animals detect objects by hearing echoes by emitting sound sent7: an echo must occur in order to be heard sent8: hearing is a kind of sense sent9: hunting requires sensing prey.
hypothesis: bats must emit sound in order to hunt their prey