Which of the animals dogs, cats, dolphins and bats can hear the lowest frequency?

Copy and complete by filling in the gaps. Choose from the words in the list.

Sound is made by vibrations. Air particles are made to vibrate. These vibrations travel through the air at a speed of about ____ $\mathrm{m}/\mathrm{s}$. When the vibrations reach your ear they make your _____ vibrate. This makes the tiny bones called _____ vibrate. The vibrations are passed on further inside the ear. When they reach the nerve, ______ signals are sent to the brain. We hear these signals as sound.