The blastula precedes the formation of the in which the germ layers of the embryo form.

In humans, all the three germinal layers are derived from:

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$