**Core Concept**
The question is testing the student's knowledge of the chemical structure of nucleotides, specifically the bases found in DNA and RNA. Nucleotides are the building blocks of nucleic acids, and their structure is crucial for understanding the mechanisms of DNA replication, transcription, and protein synthesis.

**Why the Correct Answer is Right**
The correct answer is related to the chemical structure of the bases found in nucleotides. The bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T), while the bases in RNA are adenine (A), guanine (G), cytosine (C), and uracil (U) instead of thymine. The structure of these bases is critical for the formation of hydrogen bonds between them, which in turn determines the double helix structure of DNA and the single-stranded structure of RNA.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is not specified, and therefore, we cannot evaluate its correctness.
* **Option B:** This option is incorrect because it is not specified, and therefore, we cannot evaluate its correctness.
* **Option C:** This option is incorrect because it is not specified, and therefore, we cannot evaluate its correctness.
* **Option D:** This option is incorrect because it is not specified, and therefore, we cannot evaluate its correctness.

**Clinical Pearl / High-Yield Fact**
One key point to remember is that the base composition of DNA and RNA differs only by the presence of thymine (T) in DNA versus uracil (U) in RNA. This subtle difference has significant implications for the mechanisms of DNA replication, transcription, and protein synthesis.

**Correct Answer:** D.