An atom that is electrically neutral contains
a. more electrons than protons.
b. more neutrons than electrons.
c. an equal number of neutrons and protons.
d. an equal number of protons and electrons.

D. I wouldn't bother much with B and C since neutron doesn't necessarily has to be in the picture. So, why D? reasons being, an atom will not be electrically neutral if it exists as an ion. In other words, the no. of electrons have to be the same with the no. of protons.

3 significant figures