The four variables that must be controlled for the results of Maria and Elena to be valid are
Variables in an experiment are those values that can change.
When conducting an experiment, there are usually different types of variables that are used and one of such is the Controlled variables.
The Controlled variables are known as those extraneous variables that can affect the results ( dependent variables) of an experiment. Therefore they should be held constant in order to obtain a valid result.
Examples of such controlled variables are Temperature, Amount of light,
Humidity and Time.
Take for instance, If the experiment conducted by Maria and Elena has to do with the rate at which an enzyme acts on different substrates. The temperature of the experiment needs to be constantly maintained to achieve a valid result.
This is because an increased temperature leads to increased rate of reaction between the enzyme and the substrate.
Therefore the variables that must be controlled for Maria and Elena results to be valid are the controlled variables which includes Temperature, Amount of light, Humidity, Time.
Learn more here:
https://brainly.com/question/18042457
