An argument asserts: "The new streetlights installed in downtown have significantly reduced nighttime crime rates, proving their effectiveness." What unstated assumption is most critical to this argument's conclusion?

The correct answer to the question "An argument asserts: "The new streetlights installed in downtown have significantly reduced nighttime crime rates, proving their effectiveness." What unstated assumption is most critical to this argument's conclusion?" is Option B: Crime rates would not have decreased in the absence of the new streetlights..

The other options — A) The streetlights are aesthetically pleasing and contribute to urban beautification., C) Other cities have also implemented similar streetlighting programs with positive results., D) The cost of installing and maintaining the streetlights was financially justifiable. — are incorrect for this GRE Exam Prep question. As explained above: The argument assumes a direct causal link, overlooking other potential factors that might have contributed to the decrease in crime. This is a classic 'post hoc ergo propter hoc' fallacy.