Answer:
Fossil > Arrow Head > Pottery > Shell > Fishbone > Fish Hook
Step-by-step explanation:
Arrowhead = ___20___ feet
Fishbone = __-10___ feet
Fish Hook = ___-40__ feet
Fossil = __30___ feet
Pottery = ___10___ feet
Shell = ____0___ feet
If something is above sea level, it would have a positive elevation, and if below sea level, a negative elevation. And at sea level, you have 0 elevation.
After this, just put them in order of decreasing elevation. So, the highest elevation is 30ft with the fossil, then 20 with the arrow head, pottery at 10, shell at 0, fishbone at -10, fish hook at -40.