The option that is an example of gene expression is:
C. A cell synthesizes the protein immunoglobulin G from DNA.
Gene expression is the process by which information from a gene is used to synthesize a functional gene product, such as a protein or RNA molecule. In option C, a cell is using the information from DNA to synthesize a specific protein, immunoglobulin G. This is an example of gene expression.
Option A describes protein breakdown, which is not directly related to gene expression. Option B describes a repressor protein blocking translation, which is related to gene regulation rather than gene expression. Option D describes the role of rRNA in protein synthesis, but not specifically the process of gene expression.