Which hormone inhibits the menstrual cycle in females during the period of lactation?

Signals for parturition originate from:

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:

The signals for parturition originate from which of the following?

Select the correct path of flow of milk during breast feeding.

Explain the process of lactation.