Final answer:
The nucleus is a tiny, dense, central core of the atom with a positive charge, made up of closely packed protons and neutrons.
Step-by-step explanation:
The nucleus of an atom can be described as a tiny, dense, central core and is the positively charged region at the center of the atom. It is made up of protons, which have a positive electric charge, and neutrons, which have a neutral charge. These subatomic particles are packed tightly together, constituting nearly all the atom's mass. The correct answer to the question is a. dense, positively charged, as most objects on an atomic level are neutral overall, but the nucleus itself is positive due to the protons. Surrounding this nucleus, the atom is mostly empty space with electrons, which are negatively charged, orbiting around it.