In electrolysis, electricity is run through water to separate the _____ and _____ atoms. A:hydrogen, oxygen B:hydrogen, 点我阅读全文
A raging river contains ____ energy ____a small stream. A:same, with B:less, than C:more, than D:all possibilities above 点我阅读全文
Landfills and farms can have high concentrations of _____ which is hydrogen-rich chemical compound. A:hydrocarbon B:oxyg 点我阅读全文