sentences: echo is when sound reflects off of a surface & a sound must first be emitted before it can reflect off of a surface ->  a sound must be emitted for an echo to occur  echolocation is when some animals detect objects by hearing echoes by emitting sound & an echo must occur in order to be heard ->  echolocation requires echos to occur  a sound must be emitted for an echo to occur & echolocation requires echos to occur ->  a sound must be emitted in order for an animal to echolocate  a bat is a kind of animal & bats find their prey by sensing echos ->  bats are a kind of animal that finds their prey by sensing echos  bats are a kind of animal that finds their prey by sensing echos & echolocation is when some animals detect objects by hearing echoes by emitting sound ->  bats find their prey by using echolocation  a sound must be emitted in order for an animal to echolocate & bats find their prey by using echolocation ->  bats must emit sound in order to echolocate  hearing is a kind of sense & hunting requires sensing prey ->  hearing can be used for hunting prey  hearing can be used for hunting prey & hearing is used for sensing sounds by animals ->  sensing sounds can be used for hunting prey  sensing sounds can be used for hunting prey & a bat is a kind of animal0 ->  sensing echos can be used for hunting prey  sensing echos can be used for hunting prey & echolocation is when some animals detect objects by hearing echoes by emitting sound -> a sound must be emitted for an echo to occur0: echolocation can be used for hunting prey  a sound must be emitted for an echo to occur0 & bats must emit sound in order to echolocate -> bats must emit sound in order to hunt their prey