The blastula stage lacks which of the following?

Gastrulation is the process which involves the differentiation of the following layers in a vertebrate embryo.

Match the following with respect to stages of embryonic development in human.

Column $I$	Column $II$
$a$. Fully formed morula	$i$. By end of $7^{\text{th}}$ day after fertilization
$b$. Fully formed blastocyst	$ii$. $15$ days after fertilization
$c$. Completion of implantation process	$iii$. By end of $4^{\text{th}}$ day after fertilization
$d$. Fully formed gastrula	$iv$. By end of $10^{\text{th}}$ day after fertilization

Choose the correct option-

Assertion : After ovulation,the Graafian follicle transforms into corpus luteum.
Reason : The corpus luteum secretes a large amount of progesterone.

Which one of the following is not the function of placenta?

Which of the following secretes the hormone relaxin during the later phase of pregnancy?