Final answer:
Option (A), Introns are non-coding stretches of DNA interspersed among exons in eukaryotic genes, which are removed from pre-mRNA during splicing.
Step-by-step explanation:
In a standard eukaryotic gene, the stretches of DNA that are interspersed among exons are called introns. These are the non-coding sequences that do not encode for functional proteins and are removed from the pre-mRNA during processing.
The process of removing introns and reconnecting exons is called splicing, which must be precise to prevent a shift in the reading frame and ensure the production of functional proteins. Introns can be involved in gene regulation and add complexity to genetic processing. Not only do they allow for alternative splicing, which can result in multiple proteins from a single gene, but they can also contain regulatory elements.