In which of the following is holoblastic cleavage observed?

Ovulation can be detected by

Select the correct sequence of events in human reproduction.

In which of the following are megalecithal (macrolecithal) eggs found?

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:

Give differences between:
$(a)$ Testis and ovary
$(b)$ Sperm cell and ovum (egg) cell