Final answer:
Epigenetic inheritance involves heritable changes in gene expression without altering the DNA sequence, such as the covalent modification of DNA bases, notably DNA methylation, and histone modifications. Therefore, the correct option is A.
Step-by-step explanation:
The structure that shows epigenetic inheritance is a covalent modification of DNA base. Epigenetic inheritance refers to the heritable changes in gene expression that do not involve alterations to the underlying DNA sequence. Such changes can include the addition of methyl groups to the DNA, often at cytosine nucleotides, which can result in gene silencing.
Additionally, modifications of histone proteins through methylation, acetylation, and phosphorylation also represent epigenetic mechanisms. These modifications affect the packing state of DNA, influencing the accessibility of genes for transcription and can be transmitted through cell divisions, influencing the attribute of heritability in epigenetic regulation.