A student make a model of a river in a sandbox. A pile of sand represents soil and bits of rock in the riverbed. Water pouring from a hose represents river water as it flows downhill. Which two characters are limitations of the students model?
A. The model is missing plants, fish , and other details found in a real river.
B. The model soil is nothing like the soil found in a real riverbed
C. The model is much smaller than a real river .
D. The model river water flows downhill instead of uphill like real river water does.