Concept:Oestrogen controls female sexual characteristics and the reproductive cycle, while milk let-down is controlled by a different hormone, oxytocin.
Explanation:Oestrogen is responsible for the development of secondary sexual characteristics in female animals.
It also brings about the onset of the heat period.
Oestrogen promotes the development of the udder during pregnancy.
Milk let-down after parturition is caused by the hormone oxytocin, not by oestrogen.
Hence, oestrogen is not responsible for milk let-down after parturition.
Answer:C. milk let-down after parturition