Observe the given figure carefully and identify the site of fertilization by considering the parts labeled as $a, b, c,$ and $d$.

$A$ female of $24$ years age attained puberty at the age of $14$ years. She has two children born by normal delivery. How many polar bodies are formed in her body till date $($each $\text{M.C.}$ is of $30$ days$)$ :-

The prepubertal period refers to a stage of

Pick the $ODD$ homologous pair out.

An egg with yolk in the center and cytoplasm surrounding it is known as:

Fraternal twins are produced when