The 5′ base in the left strand is part of a base pair that is colored gray and is on the bottom. The 3′ base in the left
strand is part of a base pair that is colored black and is on the top. (A) 5′-GG-3′/3′-UU-5′; (B) 5′-GU-3′/3′-UG-5′; (C) 5′-UG-3′/3′-GU-5′; (D) 5′-GG-3′/3′-UC-5′; (E) 5′-GC-3′/3′-CG-5′