Answer:
The answer is B "because Gitlow's legal rights were used to interpret the issue of incorporation"
Step-by-step explanation:
We can eliminate the bottom two options because they have nothing to do with "due process".
The Supreme Court used the due process clause to interpret the issue of incorporation "Nor shall any State deprive any person of life, liberty, or property, without due process of law;". This statement also has no relation to a person's citizenship status; therefore the answer is B.
Hope that helps :)