The lightest elements in the primitive universe are hydrogen and helium. Slightly heavier elements such as carbon are only formed in the nuclear reaction of the planet and will be dispersed when the planet explodes. Although the age of the universe does not exceed two billion Years, but recently discovered gas clouds contain carbon elements billions of years ago. Based on the above views, which of the following is true? ? ['Primitive planet contains only hydrogen.', 'Some planets were formed before the universe reached two billion years of age.', 'The carbon in the gas cloud later formed some parts of the planet.', 'The planet that determines the time is not the same as the gas cloud.']