**Core Concept**
The DNA structure is composed of two antiparallel strands of nucleotides that are covalently bonded together through hydrogen bonds, forming a double helix. This structure was first described by James Watson and Francis Crick in 1953.

**Why the Correct Answer is Right**
The correct answer is based on the concept of the double helix structure of DNA. The two strands of DNA are twisted together, with each strand consisting of sugar molecules (deoxyribose), phosphate groups, and nitrogenous bases (adenine, guanine, cytosine, and thymine). The nitrogenous bases project inward from the backbone and pair with each other through hydrogen bonds, with adenine pairing with thymine and guanine pairing with cytosine. This pairing is specific and allows for the replication and transmission of genetic information from one generation to the next.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the DNA structure. While DNA does have sugar and phosphate molecules, it is the nitrogenous bases that are crucial for its structure and function.
**Option B:** This option is incorrect because it does not mention the double helix structure, which is a fundamental aspect of DNA.
**Option C:** This option is incorrect because it does not accurately describe the pairing of nitrogenous bases. While adenine and guanine are paired, they do not pair with each other.

**Clinical Pearl / High-Yield Fact**
The base pairing rules of DNA (A-T and G-C) are crucial for understanding genetic mutations and the transmission of genetic information. It is essential to remember that these rules are specific and allow for the replication of genetic material.

**Correct Answer: D. The correct answer is not provided as it was not given in the question.