Final answer:
The renal capsule is an example of a specular reflector because of its smooth surface that reflects light.
Step-by-step explanation:
A specular reflector refers to an object or surface that reflects light in a specific direction, such as a mirror. Among the options given, the only example of a specular reflector is the renal capsule (option a). The renal capsule is a transparent, fibrous membrane that surrounds the kidney and has a smooth surface that reflects light.