Given below are a few statements related to gene regulation in prokaryotes:

A. In prokaryotic operons, the operator region is located upstream of the promoter region.

B. Positive control mechanisms involve activator proteins that enhance the binding of RNA polymerase to the promoter.

C. Attenuation is a regulatory mechanism seen in operons controlling the synthesis of amino acids like tryptophan.

D. In prokaryotic cells, all genes in an operon are transcribed as separate mRNAs with individual regulatory controls.

Which one of the following options represents a combination of all correct statements?