An atomic nucleus is composed of a) protons. b) protons and neutrons. c) protons and electrons. d) protons, neutrons, and electrons.

B)protons and neutrons.

Explanation:

The protons and neutrons are located in the nucleus of the atom and represent most of the 'mass' of the atom, that's their count that determine the 'mass' of an atom (like 12 for Carbon).

The electrons rotate around the nucleus and have a negligible mass.

which statement about this sum is true? −245+2.7

i don't understand. explain it clearly