(A) doesn’t help us make any claims about what will happen in the future. We still have no reason to believe the advocates’ prediction about the future.

(B) doesn’t help us make any claims about the future. We still have no reason to believe the advocates’ prediction about the future.

(C) provides a reason to think that geothermal power plants won’t be built. This doesn’t support a prediction that power from geothermal power plants will be available in most areas.

(D) provides a reason to think that in the future, power from geothermal power plants will be more available. If future drills allow deeper and more economical drilling, then we have reason to think geothermal power plants will be viable in a larger range of areas, because they’ll be able to access underground hot water and steam in places that they currently can’t.

(E) gives us reason to think that productions costs for almost all power plants will go down in the future. But that doesn’t help us support a prediction that geothermal power plants will be available in most areas in the near future. The current constraint on these power plants isn’t necessarily their production costs, but rather the ability to reach underground hot water and steam through drilling.