Explanation

• hydrogen gas can not use as fuel
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• "AS " is best to keep the meaning of the original sentence
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• TWO REASONS WHY WE USE THE "AS" PREPOSITION IN THE ABOVE SENTENCE

• 1: We use as with a noun to refer to the role or purpose of a person or thing:
• Fuel is a noun 
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• 2: "AS" preposition is used in those sentences in which two things indicate the same meaning or use the same purpose
• For example 
• Hydrogen can also serve as fuel. 
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