The correct option is A A large fraction of species faces the threat of becoming extinct even before we discover them
Robert May’s estimate
His estimates state that only (22%) of the existing species on earth have been described so far and the rest are yet to be identified.
This indicates that around 6 million species are yet to be discovered and named.
Biodiversity loss
According to the IUCN Red list, around 784 species have become extinct in the last 500 years with nearly 27 species becoming extinct in the last 20 years alone.
To add to the worries, more than 15,500 of identified species throughout the world are facing the threat of extinction.
Meaning of the statement
Thus, the given statement means that with the current rate of biodiversity loss, it is highly probable that quite a large number of unidentified species are facing the threat of extinction, even before they can be discovered.
Final answer
(C) A large fraction of species faces the threat of becoming extinct even before we discover them.