Which one of the following has the highest number of species in nature?

Given below are pie diagrams $A, B$ and $C$ related to the proportionate number of species of major taxa of invertebrates,vertebrates,and plants,respectively. Critically study and fill in the blanks $I, II, III$ and $IV$.

How do scientists extrapolate the total number of species on Earth?

Which one of the following has the highest number of species in nature?

What percentage of the total global species diversity does India possess (in $,\%$)?

India has much of its land area in the $\underline {i}$ and possesses more than $\underline {ii}$ species of birds.