A. Renaturing

B. Denaturing

C. The routine agarose gel

D. The routine polyacrylamide gel

Explanation: In the case of single-stranded molecules, denaturing gels are used. It is so because, if denaturing gels are not there, there are chances of formation of secondary structures which hinder the movement of nucleic acids. Thus to avoid this, denaturing agents such as urea, etc. are added.