1. What Number might be a good representation for the sea level? 2. How do represent the distance below and above the sea level? 3. How far is the cliff from the sea level? 4. How far is the bird from the sea level? 5. How far is the crab from the sea level? 6. What is the distance between the cliff and the crab? 7. What is the distance between the bird and the crab?