Question

What happens during a controlled experiment?

No observations are made.


A factor called a prediction is changed.


Many variables are changed at once.


The results of changing the independent variable are observed

Answer 1

Explanation:

The answer is that 1 variable is allowed to change. The others are held at a constant.

An example would be the growth of a poinsettia. These Christmas plants are very touchy. They respond badly to too much water or not enough water. So you keep the amount of dirt, the amount of sunlight, the amount of support that each plant receives as a constant.

The amount of water is what you change in one of the plants. The one plant (or a few) will measure the growth of the plant.

So the last answer is the one you want.