Exam LSAT Section 1 Logical Reasoning topic 1 question 115 discussion

Actual exam question from Test Prep's LSAT Section 1 Logical Reasoning

Question #: 115
Topic #: 1

[All LSAT Section 1 Logical Reasoning Questions]

Quasarscelestial objects so far away that their light takes at least 500 million years to reach Earthhave been seen since 1963. For anything that far away to appear from Earth the way quasars do, it would have to burn steadily at a rate that produces more light than 90 billion suns would produce. But nothing that burns at a rate that produces that much light could exist for more than about 100 million years.
If the statements above are true, which one of the following must also be true on the basis of them?

A. Instruments in use before 1963 were not sensitive enough to permit quasars to be seen.
B. Light from quasars first began reaching Earth in 1963.
C. Anything that, from Earth appears as bright as a quasar does must produce more light than would be produced by 90 billion suns.
D. Nothing that is as far from Earth as quasars are can continue to exist for more than about 100 million years.
E. No quasar that has ever been seen from Earth exists any longer.

Show Suggested Answer

Suggested Answer: E 🗳️
Heres a rare Inference question thats vulnerable to prephrasing: Quasars burn so hot that they cant last for more than 100 million years, but light from quasars takes at least 500 million years to get here. Quasars have only been seen since 1963, and so any quasar light that anyone on Earth has seen has to be at least
500 million years old, and so, as E. points out, that quasar itself cannot exist any more. By the time its light hits us, its been dead for at least 400 million years.

by [deleted] at March 9, 2025, 1:26 p.m.

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