Final answer:
The basic unit of matter is the atom, the smallest component of an element that retains its properties. option a is correct.
Step-by-step explanation:
The basic unit of matter is an atom. An atom is the smallest component of an element that still retains the properties of that element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms, which are incredibly small—typically around 100 picometers in size.
Atoms consist of a dense central nucleus surrounded by a cloud of negatively charged electrons. When atoms of the same element come together, they form molecules, which are combinations of two or more atoms held together by chemical bonds. Therefore, the correct answer to the student's question is A. atom.
The basic unit of matter is the atom. Atoms are the smallest indivisible units of an element, and they combine to form molecules, which can be further organized into larger structures like compounds. A molecule is a group of atoms bonded together, and a compound is a substance composed of two or more different elements chemically combined in fixed ratios. Gas, on the other hand, is a state of matter, not a fundamental unit of matter.