**Core Concept**
The question is testing the student's understanding of the composition of protons and neutrons in atomic nuclei. Protons and neutrons are subatomic particles that reside in the nucleus of an atom and are composed of even smaller particles called quarks. Specifically, protons are made up of 2 up quarks and 1 down quark, while neutrons are composed of 2 down quarks and 1 up quark.

**Why the Correct Answer is Right**
The composition of protons and neutrons is based on the quark model, which was first proposed by physicists Murray Gell-Mann and George Zweig in the 1960s. According to this model, protons and neutrons are made up of 3 quarks each, with protons consisting of 2 up quarks and 1 down quark, and neutrons consisting of 2 down quarks and 1 up quark. This quark composition determines the properties of protons and neutrons, including their mass, charge, and spin.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the composition of protons and neutrons.
**Option B:** This option is incorrect because it suggests a different quark composition for protons and neutrons.
**Option D:** This option is incorrect because it suggests a different quark composition for protons and neutrons.

**Clinical Pearl / High-Yield Fact**
The quark model is a fundamental concept in particle physics that helps explain the properties of subatomic particles like protons and neutrons. Understanding the quark composition of these particles is essential for describing the behavior of atomic nuclei in chemistry and physics.

**Correct Answer:** C.