13 billion years ago, what did the universe use to start nuclear fusion?

The cosmic background radiation provides direct evidence that the universe did expand from a dense, hot state, for this is the condition needed to produce the radiation. In the dense, hot early universe thermonuclear reactions produced elements heavier than hydrogen, including deuterium, helium and lithium.

Explanation:

people flirt to show their affection towards someone in a less forward way then telling. they want the other person to guess what they’re feeling to have the other person also start to like them