Where is the greatest biodiversity on Earth found?

What is the full form of $IUCN$?

Who proposed the 'Rivet Popper Hypothesis'?

At one time,tropical rainforests covered more than $..........$ of the earth's land surface,but now they do not cover more than $..........$.

Initially $A$ biodiversity hot spots were identified but subsequently nine more have been added to the list,bringing the total number of biodiversity hot spots in the world to $B$. These hot spots are the regions of accelerated habitat loss. Three of these hot spots—Western Ghats and Sri Lanka,Indo-Burma,and Himalaya—cover our country's exceptionally high biodiversity regions. Although all the biodiversity hot spots put together cover less than $C$ $\%$ of the earth's land area,the number of species they collectively harbour is extremely high,and the strict protection of these hot spots could reduce the ongoing mass extinctions by almost $D$ $\%$. $A, B, C$ and $D$ in the paragraph refer to:

India covers the world land area of . . . . . . and contributes the global diversity of . . . . . . .