It is reported that Tuvalu, a South Pacific island country, was forced to immigrate to New Zealand. At present, scientists are committed to studying the combination of carbon dioxide.

According to CO2+4H2→ energy +2H2O, each molecule in this energy contains 1 carbon atoms and 4 hydrogen atoms. When n= 1, the chemical formula in option A is CH4, which is consistent with the meaning of the question.

Options b, c and d do not meet the problem.

So choose: a.