How Do the NTPs Enter RNA Polymerase

How do the NTPs enter RNA polymerase?

A) base-paired with the incoming (downstream) DNA
B) with the incoming DNA but not base-paired with it
C) from the exit site, as the DNA leaves the enzymes, the NTPs move in the opposite
Direction
D) through a funnel-like channel sized just for NTPs
E) there is no specific way, any of the above routes are used