Of whatever reasons, I would not agree that we can prove A to be incorrect by putting numbers.
I eliminated A because it is too negative. The word "dramatically" means unexpected or sudden change. It is not practical to say "The cost of oil has fallen dramatically in the last decade". A decade is a longer period of time to say dramatic increase or decrease.
Threshold = Cost of Solar - Cost Of Oil (Assume Profit is same in both the cases)
T = S - O
Now since my T is constant, S and O should either increase or decrease together to same extent.
As per the premise, S has become "far more cost-efficient in the last decade", it doesn't use any strong word like "dramatically" , "extraordinarily" , "unexpectedly" etc, So O should keep pace with S.
In such case, C sounds a better option, as the reason for cost-efficiency is common.
A could be correct, had it been simply "The cost of oil has fallen"
I eliminated A because it is too negative. The word "dramatically" means unexpected or sudden change. It is not practical to say "The cost of oil has fallen dramatically in the last decade". A decade is a longer period of time to say dramatic increase or decrease.
Threshold = Cost of Solar - Cost Of Oil (Assume Profit is same in both the cases)
T = S - O
Now since my T is constant, S and O should either increase or decrease together to same extent.
As per the premise, S has become "far more cost-efficient in the last decade", it doesn't use any strong word like "dramatically" , "extraordinarily" , "unexpectedly" etc, So O should keep pace with S.
In such case, C sounds a better option, as the reason for cost-efficiency is common.
A could be correct, had it been simply "The cost of oil has fallen"