sentence2_structure: Fracking<>delivers<>natural gas<>from rock$$$rock<>might not otherwise be<>obtainable
sentence1: A campaign in the United Kingdom aimed to prevent the commencing of a controversial method of shale gas extraction known as fracking have organised themselves under the name Frack Off.
sentence2: Fracking delivers natural gas from rock that might not otherwise be obtainable.
question: What delivers natural gas from rock that might not otherwise be obtainable?