Final answer:
The Innermost Stable Circular Orbit (ISCO) is the closest orbit around a black hole where matter can stably orbit without being pulled into the black hole or being ejected. The correct answer is: b) Matter can stably orbit a black hole inside the ISCO.
Step-by-step explanation:
The Innermost Stable Circular Orbit (ISCO) holds significant importance in the dynamics of matter around a black hole. The correct answer is: b) Matter can stably orbit a black hole inside the ISCO. The ISCO is the closest orbit around a black hole at which a particle can stably maintain a circular orbit. Inside the ISCO, any further inward motion would inevitably lead to the particle's plunge into the black hole. This orbit is crucial in understanding the behavior of matter in extreme gravitational environments. It represents a boundary between stable and unstable orbits, influencing the fate of material in close proximity to the black hole. As matter approaches or enters the ISCO, gravitational forces become increasingly dominant, and the dynamics become more challenging to predict, often resulting in eventual accretion onto the black hole.