Answer :
Bats use high frequency. Whenever somebody says a quantity is "high",
you have to ask "compared to what ?". In this case, it's compared to human
hearing ... we can't hear bats at all, or if we can, it just sounds like a 'click'.
you have to ask "compared to what ?". In this case, it's compared to human
hearing ... we can't hear bats at all, or if we can, it just sounds like a 'click'.