The independent variable is the the force acting on the wagon; option B.
Variables are factors in an experiment which can be changes and these changes results in changes in the result of the experiment.
There are three types of variables, they are:
Considering the experiment by the student, independent variable is the the force acting on the wagon since changes in the force on the wagon will result in changes in the acceleration of the wagon.
In conclusion, the independent variable produces changes in the dependent variable when it is changed.
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