Final answer:
The correct answer to the student's question is C) epigenetics, which studies heritable changes in gene expression that do not involve alterations to the DNA sequence.
Step-by-step explanation:
The study of heritable changes in gene expression that occur without a change in the DNA sequence is known as C) epigenetics. Epigenetic mechanisms, such as DNA methylation and histone modification, influence gene activity and structure, resulting in variations in gene expression that can be passed down to subsequent generations without altering the underlying genetic code. Such epigenetic modifications can be influenced by environmental factors and lifestyle choices, potentially affecting not only individuals but their offspring as well.