Which of the following is the best definition of an atom?
O
A. A positively charged particle
3. A negatively charged particle
C. The basic unit of all living things
O
D. The basic unit of matter

The basic unit of matter

Explanation:

An atom is the smallest unit of an element or any matter that can ever exist and still retain the properties of that matter. So, since matter could exist as gases, liquids or solids - atoms serves as the basic unit of matter.

Furthermore, an atom is neither a positively charged nor a negatively charged particle rather it is neutral (with no charge).

As well, it is a cell that is regarded as the basic unit of all living things, not an atom

Thus, an atom is best described as the basic unit of matter whether living or non-living.

carbon atoms, hydrogen, oxygen, and nitrogen.