The $Oestrus$ cycle is a characteristic of which of the following?

Match the columns.

Column-$I$	Column-$II$
$(a)$ Parturition	$(p)$ Attachment of embryo to endometrium
$(b)$ Gestation	$(q)$ Release of egg from Graafian follicle
$(c)$ Ovulation	$(r)$ Delivery of Foetus from uterus
$(d)$ Implantation	$(s)$ Duration between pregnancy and birth
	$(t)$ Formation of zygote by fusion of egg and sperm

Secretion of large quantities of estrogen causes:

If the nuclei from an $8$-celled stage of an embryo are transplanted into enucleated eggs,which of the following events is likely to occur?

The figure shows a section of human ovary. Select the option which gives the correct identification of either $A$ or $B$ with function/characteristic.

Rapid secretion of $LH$ in ovulation causes