Final answer:
All matter in the universe is composed of atoms, which are the smallest units that retain all of an element's properties. Atoms can combine to form molecules, which are the chemical building blocks of matter.
Step-by-step explanation:
The correct answer to the question is d) atoms. All matter in the universe is composed of extremely small particles called atoms. Atoms are the basic building blocks of matter and everything around us is made from different types of atoms. For example, a single oxygen atom has all the properties associated with the element oxygen, such as supporting combustion.
While atoms are the smallest units that retain all the chemical properties of an element, they can also combine to form molecules. Molecules are two or more atoms joined together. These molecules can vary greatly in size and complexity, ranging from diatomic molecules like oxygen (O2) to large biomolecules like proteins or DNA.
Even though atoms combine to form cells, tissues, and ultimately living organisms, it is the atoms themselves that are the fundamental components of all matter. Whether we are considering a star, a rock, or a living cell, everything is ultimately built from atoms.