The correct answer for the question "Seed dormancy is regulated by" is option 1, Abscisic acid. Seed dormancy refers to a period of time in which a seed remains inactive and does not germinate. Abscisic acid, also known as ABA, is a plant hormone that plays a crucial role in regulating seed dormancy. It inhibits seed germination by suppressing the growth of the embryo and maintaining a state of dormancy. Abscisic acid also helps in preventing premature germination during unfavorable environmental conditions, such as drought or extreme temperatures, by inhibiting the synthesis of growth-promoting hormones like gibberellic acid. Therefore, option 1, absicisic acid, is the correct answer as it is the key regulator of seed dormantcy.