What is the nucleus held together by?

A. the attraction between the quarks in the proton and neutrons

B. the attraction between the electrons inside the nucleus

C. the electromagnetic attraction between two neutrons

D. the electromagnetic attraction between two protons

The correct answer would be A.

Explanation:

The fundamental particles of both neutrons and protons are called quarks. Inside the nucleus are neutrons and protons. So for the nucleus to be held together, bothe the (neu) trons and (pro) tons have to attract, and thus being the fundamental particles, the quarks also have to attract.