What Is Thought to Occur When CRP Binds to DNA

What is thought to occur when CRP binds to DNA?

A) formation of a hairpin that prevents progression of RNA polymerase
B) bending of DNA to facilitate RNA polymerase binding
C) blocking of promoter regions to prevent binding of RNA polymerase
D) forms non-covalent interactions with RNA polymerase to bind it to DNA
E) none of the above