Hydrogen naturally exists as Cloze (1): JXUwMDM5JXUwMDQxJXUwMDRkJXUwMDAyJXUwMDAzJXUwMDA5JXUwMDA2JXUwMDE2JXUwMDE5JXUw MDBkJXUwMDEz gas, where each molecule is made up of Cloze (2): JXUwMDJjJXUwMDAzJXUwMDE4JXUwMDRmJXUwMDQxJXUwMDE1JXUwMDFiJXUwMDAyJXUwMDFl .In petrol and diesel cars, the burning of fuel produces Cloze (3): JXUwMDNiJXUwMDAyJXUwMDEzJXUwMDEwJXUwMDBkJXUwMDAxJXUwMDRlJXUwMDQ0JXUwMDBkJXUw MDA2JXUwMDE3JXUwMDExJXUwMDBkJXUwMDAx and Cloze (4): JXUwMDJmJXUwMDE2JXUwMDE1JXUwMDExJXUwMDE3JXUwMDVj