Why does life in the sahara cluster around oases?
a.
oases have good roads and infrastructure.
b.
the climate at oases is cooler.
c.
oases offer a supply of water.
d.
there are many job opportunities near oases.

Life in the Sahara cluster around oases because it offers a supply of water.  

Option C  

Explanation:

Oasis gets formed when there is an availability of surface water or a source of water under the ground. Because of rock accumulation in the desert, water cannot be seen. So, oasis plays a vital role in providing food and productive growth to plants.  

This also acts as a stop for traders who travel along it to fill their foods. The knowledge about the oasis locality in the desert seems to be important for exportation purposes. Eg: the oases in Ghadames, Libya.  

because money talks, money is power. by limiting a person income potential, you limit their overall potential.

explanation:

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.