Assertion: natural gas's form | /r/HasProperty | developed
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Source sentences:
text: While the Nation's overall energy history is one of significant change as new forms of energy were developed, the three major fossil fuelspetroleum, natural gas, and coal, which together provided an average of 87% of total U.S. primary energy use over the past decadehave dominated the U.S. fuel mix for well over 100 years