Answer: Repeating units of phosphate and deoxyribose form the backbone of DNA.
Explanation:
The three main structural components of a nucleotide is
1. a nitrogenous base
2. a five-carbon sugar (such as deoxyribose)
3. one to three phosphate groups
These are examples of physical properties of DNA, therefore the last answer choice would be the correct answer. The key here is to focus on which answer both describes physical properties and references the diagram (which is circling a phosphate group and a sugar).
(PS: I took the test; that answer's right)
