In the given pie chart,what do '$a$' and '$b$' represent respectively?

If the Bengal tiger becomes extinct,then . . . . . . .

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.

Match the List-$I$ with List-$II$:

List-$I$	List-$II$
$A$. Narrowly utilitarian	$i$. Hot-spot
$B$. Broadly utilitarian	$ii$. Seed bank
$C$. In situ conservation	$iii$. Photosynthesis
$D$. Ex-situ conservation	$iv$. Food and Fibre

What does '$X$' represent in the given graph?

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