The first life on earth, a simple, single-celled prokaryotic bacteria, appeared on life approximately how long ago? a) 4 thousand years b) 4 million years c) 4 billion years d)

Pls me i need this ! each cell has genes activated depending on it's job and what kind of cell it is. it is the presence of that causes the repressor protein to fall off and unblock the gene on the lac operon. if a gene is turned on then it is being an additional circular chromosome found in some bacteria that is used in genetic engineering.