Set 9: Central Ideas (Intermediate)
Explanation
PASSAGE
The following text describes an astronomical object. A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. Although it has a great effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity.
What defines the 'event horizon' of a black hole?
Detailed Explanation
This question asks you to identify the main point of the passage. Choice B is the best answer. The text explicitly states: 'The boundary of no escape is called the event horizon.' This matches Choice B.
Choice A refers to the singularity, not the event horizon.
Choice C is incorrect because black holes do not emit visible light from within the horizon.
Choice D is a theoretical consequence but not the definition provided in the text. Remember that supporting details help prove the central idea but are not the main point themselves. The author's central idea should be broad enough to encompass the entire passage while still being specific enough to be meaningful. Ask yourself what the author most wants you to understand.
Key Evidence:
• "boundary of no escape is called the event horizon"
Why others are wrong: A (Incorrect - refers to singularity), C (Contradicts text - light cannot escape), D (Unsupported - text defines it as boundary of no escape).
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