A “Butwhat began 150 years ago...” (line 7)
B “Thus,we need to aggressively look to the future...” (lines 17-18)
C “Ifthat search goes poorly —” (lines 43-44)
D “Yethuman with an economic incentive to be optimistic...” (lines 50-51)
E “On the other hand, so could advanced biofuels...” (line 57)