Which type of stimulus is used to achieve parthenogenic development?

Select the appropriate option regarding $Hydra$.

Select the correct option for the zygote.
$I -$ It is found only in organisms undergoing sexual reproduction.
$II -$ It is always diploid $(2n)$.
$III -$ It is also known as a fertilized egg.
$IV -$ It is always formed as a result of fertilization or syngamy.
$V -$ It is the link between two generations.

Choose the odd one with respect to sexuality.

$A$: Zygote is the first cell of the new generation in all sexually reproducing organisms.
$R$: Cell division and cell differentiation are the stages of embryogenesis.

........ and ........ are examples showing external fertilization.