What is the oestrous cycle?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Endometrium is necessary for implantation of blastocyst.
Reason $R$: In the absence of fertilization,the corpus luteum degenerates that causes disintegration of endometrium.
In the light of the above statements,choose the correct answer from the options given below:

Given below are the events in human reproduction. Write them in correct sequential order: Insemination,gametogenesis,fertilisation,parturition,gestation,implantation.

When the centrolecithal egg of insects undergoes regular cleavage,what is the resulting arrangement?

Gynaecomastia condition can develop due to

Match the columns.

Column $I$	Column $II$
$(a)$ Mons pubis	$(1)$ Embryo development
$(b)$ Antrum	$(2)$ Sperm cell
$(c)$ Trophoblast layer	$(3)$ External genitals of female
$(d)$ Mitochondria	$(4)$ Graafian follicle