Consider the following statements 
A. the principle of complementarity governs the process of transcription. 
B. It is a DNA sequence that provides binding site for RNA polymerase, and it is the presence of a promoter in a transcription unit that also defines the template and coding strands. 
C. There are additional regulatory sequences that may be present further upstream or downstream to the promoter of transcription unit. 
D. Jacob and Monad were first to elucidate a transcriptionally regulated system in E. coli. 
Select the correct option-