What are the fundamental units of matter called?
a. gasesb. moleculesc. atomsd. solids?

The correct answer is option C. i.e Atoms. Tthe fundamental unit of matter is an atom. Atoms are made of made of sub-atomic particles too but the smallest unit of life is considered as an atom. Atoms combine to form molecules and then molecules combine with different types of interactions to form solids, liquids or gases.

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