Epigenetics refers to a special kind of hereditary mechanism. epigenetic changes do not change the dna nucleotide sequence, yet their effect on gene expression can last for several generations. in one surprising study, it was found that the grandsons of men who suffered a famine were less likely to die of cardiovascular disease. the experience of famine made some cardio-protective change in the sperm of those grandfathers that was passed on. what type of change was likely responsible?

a. histone acetylation or dna methylation
b. phosphatase levels
c. ubiquitin tagging