Which is the correct statement about protons?
A.It is a nucleus of deuterium
B.It is an ionised hydrogen molecule
C.It is an ionised hydrogen atom
D.It is an $\alpha - particle$

Hint: Firstly by the basic rules of the proton as it is important for the desired output determination. Now these rules are, following priority order, the arrangement of the groups in the right alphabetical order for the sake of naming and to deduce the numbering by chief functional group. By following this we will get the right numbering and then we can put it in the correct sequence to get the right name.

Complete step by step answer:
In the given question we have to give out the correct naming, structure uses and basically the characteristics of the compound given in the problem statement.
The word proton is Greek for "first", and this name was given to the hydrogen nucleus by Ernest Rutherford in \[1920\] . In previous years, Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by atomic collisions.
Proton is an ionised hydrogen atom.
A hydrogen atom is made up of one proton (present in the nucleus) and one electron (present outside nucleus).
During ionisation of the hydrogen atom, the electron is lost. Hence, only protons are left out.

Note:
Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons" (particles present in atomic nuclei). One or more protons are present in the nucleus of every atom; they are a necessary part of the nucleus. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number