Answer:
It has mass but no charge.
Step-by-step explanation:
The question asks to describe ONE of the subatomic particles that could be found at location X in the model, so you should think of protons and neutrons. Now all of the answers do NOT describe a proton, but the first answer describes a neutron. Neutrons have mass but no charge. Why? The neutron has two down quarks and one up quark, down quarks, have a charge of -1/3, and up quarks have a charge of +2/3. Doing the math, you'd see that (-1/3)2+2/3 is equal to a neutral charge. So a neutron WILL have a mass, but will NOT have a charge, as they are used to hold the nucleus together.