Final answer:
The correct answer is (D) adenine, thymine, cytosine, guanine, which are the four nitrogenous bases that make up DNA nucleotides, with adenine and guanine being purines, and cytosine and thymine being pyrimidines.
Step-by-step explanation:
The nitrogenous bases that make up the nucleotides of DNA are adenine (A), thymine (T), cytosine (C), and guanine (G). Therefore, the correct answer to the student's question is (D) adenine, thymine, cytosine, guanine. These bases are categorized into two groups, with adenine (A) and guanine (G) being purines, which have a double-ring structure, and cytosine (C) and thymine (T) being pyrimidines, with a single-ring structure.
Each nucleotide in DNA consists of three components: a deoxyribose sugar, a phosphate group, and one of these four nitrogenous bases. The nucleotides link together to form the DNA double helix, with complementary base pairing of A with T and C with G, held together by hydrogen bonds.
The DNA structure is distinct from RNA, which contains uracil (U) instead of thymine.