**Core Concept**
A genomic library is a collection of cloned DNA fragments that represent the entire genome of an organism. It is a crucial tool in molecular biology, allowing researchers to study the structure and function of genes and their regulatory elements.

**Why the Correct Answer is Right**
A genomic library is created by randomly fragmenting the genomic DNA of an organism, cloning these fragments into a suitable vector, and then propagating the resulting clones in a host organism. This process allows researchers to isolate specific genes or regulatory elements of interest from the genomic library. The genomic library serves as a valuable resource for various downstream applications, including gene expression analysis, functional genomics, and genome sequencing.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be incorrect because it does not specify the nature of the genomic library. However, without more information, it is difficult to determine its inaccuracy.
**Option B:** This option could be incorrect if it implies that a genomic library is a collection of cloned mRNAs rather than genomic DNA fragments.
**Option C:** This option might be incorrect if it suggests that a genomic library is a collection of randomly assembled DNA sequences, rather than cloned DNA fragments representing the entire genome.

**Clinical Pearl / High-Yield Fact**
When working with genomic libraries, it is essential to ensure that the cloning process is efficient and unbiased to prevent the loss or underrepresentation of specific genomic regions. This can be achieved by optimizing the DNA fragmentation and cloning protocols.

**Correct Answer:** D