(I'd bet that few of us are likely to encounter a solitary soul who has actually read all of Piketty's tome.)
Nice that the meat was in the Intro to a book which only an Accounting PhD would read-through before.. grabbing a Pratchett novel for comic relief and a few endorphins for sanity.

I'll go with Door (c) too.. we Address This Matter head-on or we die-out before even the planet does (for all the other mammals too.)
It may well prove to have been the Final Test Question over all others save (saving the planet.)
Answer that one Wrongly and.. nobody much will be around to score the Test, eh?