Who made a more scientifically sound and globally accepted estimate of global species diversity?

Match the following:

Column-$I$	Column-$II$
$(P)$ Biodiversity in India	$(1) \; 45,000$
$(Q)$ Plant species in India	$(2)$ Insects
$(R)$ Most species rich group	$(3)$ Fungi
	$(4) \; 8.1\%$

According to Robert May,the total global species diversity is about:

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

Which of the following groups has the highest number of species in global biodiversity?

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 $IV$.