medium · GMAT Verbal

Passage: Black holes are regions of spacetime where gravity is so intense that nothing, not even light, can escape. According to classical general relativity, black holes are characterized by an event horizon—the boundary of no return—and a singularity at the center where density becomes infinite. However, Stephen Hawking proposed that black holes are not truly black but emit a faint glow now known as Hawking radiation. This radiation arises from quantum vacuum fluctuations near the event horizon, where pairs of virtual particles are constantly created and annihilated. If one particle falls into the black hole while the other escapes, the black hole effectively loses mass. Over unimaginably long timescales, this process leads to the evaporation of the black hole. The existence of Hawking radiation suggests a deep connection between general relativity and quantum mechanics, yet it also creates the information loss paradox: if a black hole evaporates, what happens to the physical information about the matter that fell into it? Which of the following can be inferred from the passage regarding the mass of a black hole?

1. Light contributes to a black hole's mass only if it crosses the event horizon at a speed exceeding its vacuum velocity.
2. The mass of a black hole is concentrated entirely within the virtual particles near the event horizon.
3. The total mass of the universe remains constant because escaping virtual particles eventually return to their black hole of origin.
4. As a black hole emits more Hawking radiation, the density of its central singularity decreases proportionally.
5. A black hole's mass is not necessarily permanent and can fluctuate due to quantum events at its boundary.

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