Which of the following is a plant hormone?

Insulin, thyroxin ad oestrogen are all animal hormones. Insulin is secreted by pancreas which helps In maintaining the sugar levels in a human body. Thyroxin is secreted by the thyroid gland situated in the neck. Oestrogen is the primary female sex hormone. It is responsible for the development and regulation of the female reproductive system and secondary sex characteristics. Cytokinin is a plant hormone. Cytokinins are a class of plant growth substances (phytohormones) that promote cell division, or cytokinesis, in plant roots and shoots. Hence, option D is correct.