Which description applies to alternative mrna splicing?

The answer is: processing of exons in mRNA that results in a single gene coding for multiple proteins.

RNA splicing is an important stage in gene transcription. mRNA transfers the information from DNA to proteins. In many cases, this process creates multiple proteins from the same gene by varying the exon composition. This is called alternative splicing and can happen because exons are extended or skipped, or introns can be retained instead of being removed.