The early universe contained only the lightest elements: hydrogen and helium. Heavier elements, such as carbon, were produced only when stars underwent nuclear reactions and emitted when stars exploded, and existed in subsequent gas clouds. Recently, it was found that a gas cloud contained carbon 4 billion years ago, when there were only stars less than 2 billion years old.
Which of the followings can be infered
The formation of carbon in the gas cloud does not exceed 6 billion years