Answer:
Either B or C (read the explanation)
Step-by-step explanation:
B is the largest atom of carbon.
First, B is an atom and not an ion because the negative electron charges balance out with the positive proton charges to create a balanced net charge. Additionally, we only change the number of neutrons, which are neutral.
We know B is the largest because neutrons are much larger than electrons. Therefore, an atom with the larger number of neutrons will be largest.
HOWEVER, if you're asking which atom has the larger electron cloud, C is your answer.
If there are more electrons, the pull on each electron from the protons will be less, and you can think of it as dispersing the same force across more variables. C will therefore have the largest electron cloud while D has the smallest.