Question

1. what is the purpose of a controlled variable?

to change throughout the experiment
to act as the independent variable
to remain constant to ensure the experiment is fair
to serve as the hypothesis

Explanation:

In experimental design (a key concept in Natural Science, especially in fields like Biology, Chemistry, Physics), a controlled variable is kept constant to eliminate confounding factors. This ensures that the experiment is fair (only the independent variable is intended to cause changes in the dependent variable). The first option is incorrect as controlled variables don't change. The second is wrong because the independent variable is different. The fourth is incorrect as controlled variables aren't hypotheses.

Answer:

C. To remain constant to ensure the experiment is fair (assuming the options are labeled A, B, C, D with C being the correct one as per the description)