## Core Concept
Nucleic acids, including DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are essential biomolecules that store and transmit genetic information. The structure and function of nucleic acids are fundamental to understanding genetics and molecular biology. The question tests the understanding of the basic properties and composition of nucleic acids.

## Why the Correct Answer is Right
The correct answer states that "RNA is not a double-stranded molecule in most of its forms." This is accurate because, unlike DNA which is typically double-stranded, RNA is usually single-stranded. However, without the specific options provided, we'll proceed with general knowledge about nucleic acids. DNA is double-stranded, with two complementary strands, while RNA is typically single-stranded and can form various structures, including stem-loops.

## Why Each Wrong Option is Incorrect
- **Option A:** If an option states that DNA is double-stranded, this is correct and not the answer we're looking for. DNA's double-stranded nature is a well-established fact, with the two strands being complementary to each other.
- **Option B:** If an option mentions that nucleic acids are composed of nucleotides, this is true. Nucleic acids are indeed polymers of nucleotides, each consisting of a phosphate group, a sugar (deoxyribose in DNA and ribose in RNA), and a nitrogenous base.
- **Option C:** If an option notes that RNA contains uracil, this is correct. Uracil replaces thymine in RNA, which is one of the key differences between DNA and RNA.

## Clinical Pearl / High-Yield Fact
A key point to remember is that while DNA is primarily double-stranded, RNA is usually single-stranded but can form double-stranded regions. This difference is crucial for understanding the roles and structures of DNA and RNA in cells. For example, the presence of uracil in RNA and thymine in DNA is a quick way to distinguish between the two.

## Correct Answer: D. RNA is double-stranded.