Answer:
A and D are correct
Explanation:
A is right because an atom is the basic unit of matter.
B is wrong because the atomic number is protons and electrons, not neutrons.
C is wrong because electrons do not determine what element it is, the protons do (this could be right though depending on what your teacher has taught you, but I would say it is wrong. For example, if your teacher says protons and electrons both represent the same thing, then it will be right)
D is right because the atomic number is the protons which is the basis of where it all starts.
