Answer:
the speed at which hummingbirds fly because that is actually a part of physics
An experiment or survey must be controlled in order to receive accurate results.
In an experimental group, the independent variable is changed. But in the control group, the independent variable stays the same.
I would say C! Most developing countries have high birth and death rates, while developed countries are more steady.
Where organisms are better adapted to their environments tend to survive and produce more kids!
