Which of the Following Was the First Demonstration of Epigenetics

Which of the following was the first demonstration of epigenetics?

A) Rats whose mothers were nurturing by licking and grooming their pups was associated with a gene that regulates stress response unwinding from a histone, allowing it to become active. This was associated with better coping with stress in adulthood and affected the way they nurtured their pups.
B) Humans whose background included physical abuse were likely to have a gene that regulates stress response wind more tightly on a histone, preventing it from becoming active. This was associated with withdrawal from social interactions and with more neglectful parenting of their own children.
C) Rats who were shocked the first four times they saw their mother had a gene that regulates stress response wind more tightly on a histone, preventing it from becoming active. This was associated with a lack of exploratory behavior and an overprotective relationship with their own pups.
D) Mice who were raised in the absence of other mice had a gene that regulated sociability wind from a histone, allowing it to become active. This was associated with abnormal later interactions with other mice and an inability to pass on normal socialization to their own pups.