Molecule is A. The smallest particle of a substance that retains the properties of that substance B. A atom that has a shortage of electrons in its outer orbit C. A atom that has an excessive number of electrons in its outer orbit D. A atom that flows whenever there is an imbalance of electrical charges between two points E. None of the above

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.