Questions: A variable that is changed in a scientific experiment is called (A) positive control (B) negative control (C) dependent variable (D) independent variable

The answer is (D): independent variable.

Explanation for each option:

(A) Positive control: This is a group in an experiment that receives a treatment with a known response, so it can be compared to the experimental group. It is not a variable that is changed.

(B) Negative control: This is a group in an experiment that does not receive the experimental treatment and is used to ensure that there is no effect when there should be none. It is not a variable that is changed.

(C) Dependent variable: This is the variable that is observed and measured in an experiment. It is affected by changes in the independent variable, but it is not the variable that is intentionally changed.

(D) Independent variable: This is the variable that is intentionally changed or manipulated in an experiment to observe its effect on the dependent variable. Therefore, it is the correct answer.

In summary, the variable that is changed in a scientific experiment is called the independent variable.