Answer:
The correct answer is the color of the shirt.
Step-by-step explanation:
A variable, which is controlled or changed in a scientific experiment to examine the influences on the dependent variable is known as an independent variable. As the independent variable is changed by the experimenter, the influence on the dependent variable is recorded and witnessed.
The dependent and the independent variables may be witnessed in terms of cause and effect, that is, if the independent variable is modified, then an effect is witnessed in the dependent variable. Thus, in the given case, the color of the shirt is the independent variable.