What structure is common to all five kingdoms of living organisms?
a. dna
b. nucleus
c. cell wall
d. mitochondria
i know it is not c-cell wall.

The five kingdoms of living organisms are Monera, Protista, Fungi, Plantae and Animalia. Monera is for single-celled individuals which just absorb nutrients from the cell wall. Protista is for protists, fungi is for muticellular organisms, plantae is to plants and animalia is to animals. The common structure among them is DNA> 

The proton has a positive charge while the neutron has no charge they both make up the nucleus of the atom while the elections have a negative charge and surround the nucleus of the atom. the protons and electrons are used to calculate the atom's mass whereas the neutrons don't affect the mass