Question

part a
black holes are essentially
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hint 1.
define a black hole.
very dark stars
any object with an escape velocity greater than the speed of light
the vacuum cleaners of space
not confirmed as existing

Explanation:

A black - hole is defined as an object with an escape velocity greater than the speed of light. This means that nothing, not even light, can escape from it. Dark stars is a misnomer, black - holes are not just dark stars. Saying they are "vacuum cleaners of space" is a non - scientific and metaphorical description. Black holes have been confirmed to exist through various astronomical observations.

Answer:

B. any object with an escape velocity greater than the speed of light