Answer:
d. Has a positive charge and is located in the nucleus
Memory technique:
Think of the "p" and proton and the "p" in positive.
Think of the "neu" in neutron and "neu" in neutral.
Think about electrons and electricity. Touching something "elec"tric would hurt, or give you negative feelings.
Electrons revolve around the cell while protons and neutrons are a part of the nucleus because negative and positive things would not get along.
That's all I have! I hope this helps with your studying. Happy learning, friend! :)