Answer:
I think it would be B
an independent variable is the thing that doesn't change
Explanation:
because the signal strength is what you want to stay the same you would want it to be at full bars. A is incorrect you can move the router closer or father away from the computer. your going to have to to get the best signal same for C. and on D it is incorrect because they never said that they were only going to have one device or two or three on the router.
hope this helps!