A____ consist of an inner conductor with inner diameter d, and then a concentric cylindrical insulating material around it. This is surrounded by an outer conductor, which is a concentric cylinder with an inner diameter of D. This is mostly used for high-frequency applications. This structure is well understood by taking a look at the given figure.

• A. Slot line
• B. Co-axial line
• C. Microstrip line
• D. Strip line