GMAT Critical Reasoning (CR) | Ethanol, a fuel derived from corn, can be used alone to power cars

I still am not very clear why B is the correct answer, although I see that other options are clearly incorrect.

Answer B can be interpreted in another fashion as well:
Whethermore energy is savedwhen........blah blah
a) If Yes, then Ethanol use is recommended.
b) If No, that means less energy is saved using Ethanol (either alone, or in conjunction) as compared to Gasoline. In that case, Ethanol is not recommended.

So we do get "two paths" here, and hence option B is also important
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