Read the passage and answer the question.

Nucleus of an atom is central dense mass consisting of protons and neutrons. If an atom is enlarged to the size of a classroom, the nucleus would be the size of a pinhead. In other words, an atom is almost empty. The size of a nucleus is that as compared to that of an atom.

Which of the following is true?

Nucleus is a heavy mass at the center.

The correct answer is Option 3: Nucleus is a heavy mass at the center.

• Option 1: Volume of neutron is about $$1{0^}^{12}$$ times the volume of atom. This is incorrect because a neutron is a subatomic particle found inside the nucleus, and its volume is significantly smaller than that of the entire atom.

• Option 2: Atom outside nucleus is massive. This is incorrect. The passage states that the nucleus is a "central dense mass" and that an atom is "almost empty," implying the space outside the nucleus has very little mass.

• Option 3: Nucleus is a heavy mass at the center. This is true. The passage explicitly describes the nucleus as a "central dense mass consisting of protons and neutrons".