Which of these is a disadvantage of hydrogen fuel?
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a. it is expensive to produce and transport.
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b. it works in'efficient, clean engines.
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c. it is useful for generating electricity.
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d. it is a continually available energy source.

The answer is A. It is expensive to produce and transport

Explanation:

meteorologists would compare a new weather map with one 24 h old to see how fast a front is moving.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.