The Moon appears to Earth as a small crescent, as it rotates around the Earth this expands to a full moon and back to a small crescent. This happens once every 29 days and is called a lunar month. The Moon causes the rise and fall of the ocean's tides on Earth.
A frog gets rid of it's urine through the kidneys because the heart pumps blood throughout the body, the lungs are used to take in O2 molecules and gills are use to filter out the hydrogen in HO2 so they can breathe under water. However the kidneys are part of the waste disposal system (what makes us need trip to the bathroom ever now and then) therefore that is the answer.<span />
Why people shouldn't be sent to Mars?
