Under the influence of oxytocin,which layer of the uterus exhibits strong contractions during parturition?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$ :
Assertion $A$ : Breast-feeding during the initial period of infant growth is recommended by doctors for bringing up a healthy baby.
Reason $R$ : Colostrum contains several antibodies absolutely essential to develop resistance in the newborn baby.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following contains $IgA$ antibodies?

Ovulation does not occur during the lactational period because of:

Lactational amenorrhoea is:

Oxytocin helps in