Question

a molecule is:

a. the smallest part of a substance that is not an element
b. the smallest parts of an atom
c. composed of protons and neutrinos.
d. composed of photons and protons.

Explanation:

• Option B describes subatomic particles (not molecules).
• Options C and D list particle combinations that do not form molecules; molecules are made of atoms bonded together, not protons/neutrinos/photons in these configurations.
• Option A correctly defines a molecule as the smallest unit of a non-element (compound) that retains the substance's properties.

Answer:

A. The smallest part of a substance that is not an element