Question

an atom is the smallest unit of an element that maintains its properties (with options: atom, molecule, element shown in the image)

Explanation:

The question is about identifying the smallest unit of an element that maintains its properties. In chemistry (a subfield of Natural Science), an atom is defined as the smallest unit of an element that retains the element's chemical properties. A molecule is a group of atoms bonded together, and an element is a pure substance made of one type of atom. So the correct term here is "atom".

Answer:

atom