Which statement best describes the nucleus of an atom

 J. It is centrally located structure comprising almost all of the atomic mass and having an overall positive charge.

Step-by-step explanation:

, and Number of electrons is equals to the number of protons in a particular atom.

The nucleus of an atom was is a  centrally located structure in it , discovered in 1911 by Ernest Rutherford , it consists of two sub-atomic particles 1) protons that carries positive charge and 2) neutrons that carries no charge.

It means nucleus comprising almost all of the atomic mass.

Hence, the statement best describes the nucleus of an atom  is "It is centrally located structure comprising almost all of the atomic mass and having an overall positive charge."

step-by-step explanation:

points a and b are equidistant from the desired line, so the line you find by using them will go through point r.

using points other than a and b will give the desired line only if they are equidistant from r. if they are randomly located, the perpendicular line you create will not necessarily go through point r, hence will not be a solution to the problem.