Two coaxial metallic cylinders have radii R1 and R2. The space between them is filled with a dielectric having dielectric constant r. The capacitance per metre length is

• A. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/63-1.png">
• B. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/63-2.png">
• C. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/63-3.png">
• D. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/63-4.png">