What reason does Greta Thunberg give for her claim that a low-carbon economy isn't going to work? A. because it doesn't lead to anything
B. because planting trees is good, of course, but it's nowhere near enough of what is needed
C. because our emissions have to stop, if we are to have a chance to stay below the 1.5-degree target
D. because the U. S.A. is leaving the Paris accord and that seems to outrage and worry everyone