A ray of light passes through four transparent media with refractive indices \[{{\mu }_{1}}.{{\mu }_{2}}{{\mu }_{3}},\text{ and}\,{{\mu }_{4}}\] as shown in the figure. The surfaces of all media are parallel. If the emergent ray CD is parallel to the incident ray AB, we must have [IIT-JEE (Screening) 2001]

• A. \[{{\mu }_{1}}={{\mu }_{2}}\]
• B. \[{{\mu }_{2}}={{\mu }_{3}}\]
• C. \[{{\mu }_{3}}={{\mu }_{4}}\]
• D. \[{{\mu }_{4}}={{\mu }_{1}}\]