Answer:
The answer is: A - Dimensions of the paper.
Step-by-step explanation:
"A" is the independent variable because it is the only thing that you are manipulating in each trial (i.e. folding the paper in half each time). "B" is the dependent variable because it is what you are measuring in every trial. "C" and "D" remain constant (they aren't changed at all) so they are neither dependent or independent variables.