Invertebrates were formed and active by the time of... (in $mya$)

Which of the following was $NOT$ present in a free form during the origin of life?

Which amino acid was not formed in Miller's experiment?

Explain the Big Bang theory in the context of the origin of the universe.

In his classic experiment on the formation of amino acids,Stanley Miller passed an electric discharge in a mixture of

The universe is approximately ........... years old.