sentence2_structure: Fracking<>delivers<>natural gas<>from rock$$$rock<>might not otherwise be<>obtainable
sentence1: In 2011, Crownover coauthored House Bill 3328, which required natural gas drilling operators engaged in hydraulic fracturing to disclose the chemicals used in the fracking process;
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?