The correct answer is: A. The
smallest particle of a substance that retains the properties of that substance.A molecule is a group
of two or more atoms held together by chemical bonds. The atoms in a molecule can be of the same element or of different elements. Molecules are the basic units of many substances, and they are responsible for the properties of those substances.Option B is incorrect because an atom that has a shortage of electrons in its outer orbit is called a positively charged ion. Option C is incorrect because an atom that has an excessive number of electrons in its outer orbit is called a negatively charged ion. Option D is incorrect because an atom that flows whenever there is an imbalance of electrical charges between two points is called an electric current. Option E is incorrect because it is not a valid option.