Life originated approximately how many years ago?

What was the contribution of the scientist Georges Lemaître $(1931)$?

Read the following statements and find out the correct ones:
$A.$ Spontaneous generation theory was approved once and for all.
$B.$ Pasteur showed that in pre-sterilized flasks,life did not come from killed yeast.
$C.$ Oparin observed the formation of amino acids by creating electric discharge in a closed flask.
$D.$ Life appeared $500$ million years before the formation of the earth.

The origin of life took place in/on:

Which was absent in the atmosphere at the time of origin of life?

Louis Pasteur,by careful experimentation,demonstrated that: