The particle that possesses half integral spin as
A. Photon
B. Pion
C. Proton
D. K-meson

Hint: In the given question, we need to find which particle has half integral spin. For this, we have to explain what half integral spin is. Also, accordingly, we will define the particle as well.

Complete step by step solution:
We know that the half integral spin is defined as any member of a group of particles that follow the exclusion principle, which states that only one particle of the exact same type, can exist in the same quantum state, and has a spin that really is half an odd integer. Here, we can say that a proton is a particle with a positive charge that is in the nucleus of an atom.

Thus, the Pauli Exclusion Principle constraints fermions, which are particles with half-integer spin. Bosons are particles having integer spin. Protons, neutrons, and electrons are types of fermions. So, the Pauli exclusion principle states that “in a single atom no two electrons will have an identical set or the same quantum numbers ”. In simple terms, we can say that each electron must have or be in its own unique state.

Also, there are two rules that the Pauli Exclusion Principle follows such as only two electrons can occupy the same orbital and the two electrons which are present in the same orbital should have opposite spins or they should be antiparallel to each other. Hence, the particle that possesses half integral spin as proton.

Therefore, the correct option is C.

Note: Many students write the explanation regarding protons only. But it is essential to elaborate on other terms like the Pauli Exclusion Principle, half integral spin etc. As a result, it becomes easy to understand the solution clearly.