9. Why is single-stranded RNA (ssRNA) chemically less stable than single-stranded DNA (ssDNA)? (A) ssRNA has a more rigid structure than ssDNA. (B) because Uridine is less stable than thymidine (C) ssDNA is more flexible than sSRNA. (D) SSRNA has stronger base stacking interactions than ssDNA. (E) SSRNA contains an additional hydroxyl group that makes it more reactive.