Catalyzes the transfer of the cytidylyl group of CTP to D-ribitol 5-phosphate. CTP + D-ribitol 5-phosphate + H(+) = CDP-L-ribitol + diphosphate Cell wall biogenesis; poly(ribitol phosphate) teichoic acid biosynthesis. Heterodimer together with TarJ. Belongs to the IspD/TarI cytidylyltransferase family. TarI subfamily. Truncated N-terminus.