Kate gathered three boxes of the same size made of different materials: glass, clear plastic, and aluminum painted black. She placed them on a window sill in the sun for an hour and then measured the warmth of the air in each box. In this experiment, the types of box materials are a(n) .

(a) dependent variable

(b) constant

(c) independent variable

(d) control

C. Independent variable, An independent variable is defines as the variable that is changed or controlled in a scientific experiment. ... Independent variables are the variables that the experimenter changes to test their dependent variable. A change in the independent variable directly causes a change in the dependent variable.

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