In the given pie chart representing global invertebrate diversity,what do '$x$' and '$y$' represent respectively?

Which of the following statement$(s)$ is/are correct?
$(i)$ Rich biodiversity is not essential for ecosystem health.
$(ii)$ The current rate of species extinction is $100$ to $1000$ times faster than the pre-human extinction rate.
$(iii)$ Steller's sea cow became extinct due to overexploitation by humans.
$(iv)$ Even if we combine all biodiversity hotspots,they cover less than $2 \%$ of the Earth's land area.
$(v)$ The rate of mass extinction can be completely reduced by strict protection of hotspots.

$A$: Western Ghats are included among the hot spots of biodiversity.
$R$: Western Ghats have greater amphibian diversity than Eastern Ghats.

$A$ species facing an extremely high risk of extinction in the immediate future is called:

In India, tropical wet evergreen rain forests are not found in:

Given below is the representation of the extent of global diversity of invertebrates. What groups do the four portions $(a, b, c, d)$ represent respectively?