Which of the following best describes the structure of a polymer?

The correct option is Very large molecules with repeating units linked by covalent bonds. This answer is correct because it matches the approved learning objective to describe polymers as very large molecules made from atoms linked by covalent bonds in the subtopic Polymers.

The correct option is Very large molecules with repeating units linked by covalent bonds. Very large molecules with repeating units linked by covalent bonds is correct because it directly supports the approved learning objective to describe polymers as very large molecules made from atoms linked by covalent bonds. This belongs to the subtopic Polymers within How bonding and structure are related to the properties of substances, so the explanation must stay tied to that curriculum context. The other options are incorrect because they either do not answer this learning objective, use a vague statement, or move away from Polymers.