Which is a density-independent factor in controlling a population?
a. water supply
b. disease
c. tornadoes
d. access to food

I think the correct answer from the choices listed above is option C. It would be tornadoes that is a density-independent factor in controlling a population. This is due to the reason that tornadoes are caused by natural causes which cannot be controlled by any human intervention.

The correct answer is option C, Tornadoes

Explanation:

All the three factors i.e water supply, diseases and access to foods are all density dependent variables and are expressed in the following ways:

a)Water supply – consumption of water (in litres)/acre

b)Disease – number of outbreaks /acres

c)Access to foods – tons of food produced /hectare

But tornado cannot be expressed in terms of area, but it can be expressed in terms of time i.e. number of tornadoes/year

The best choice that you can pick will be option D.