A stem-loop structure is formed in the RNA causing the polymerase to pause.

a. initiation

b. elongation

c. termination

c. termination

Explanation:

Stem-loop structure is formed as a part of Rho independent termination or intrinsic termination process in prokaryotes. The newly formed mRNA strand encounters a sequence that can base pair with itself to form a stem-loop structure. This loop is 7-20 base pairs long and is rich in Guanine and Cytosine bases. Due to strong hydrogen bonding between the GC pairs, the loop formed is very stable. A protein bound to RNA Polymerase binds to this loop and stops the enzyme from further transcribing. Stem loop structure is usually followed by a poly uracil sequence. Weak Adenine-Uracil bonds weaken the RNA-DNA duplex. The duplex unwinds and RNA Polymerase dissociates terminating transcription process.