Critical Reasoning

Researchers hope to find clues about the A'mk peoples who lived in the Kaumpta region about one thousand years ago but who left few obvious traces. The researchers plan to hire the few remaining shamans of the modern-day indigenous people in Kaumpta, who are believed to be descended from the A'mk, to lead them to ancestral sites that may be the remains of A'mk buildings or ceremonial spaces. The shamans were taught the location of such sites as part of their traditional training as youths, and their knowledge of traditional Kaumpta customs may help determine the nature of any sites the researchers find.

Which of the following is an assumption on which the success of the plan depends?

A. The researchers have reliable evidence that the A'mk of one thousand years ago built important ceremonial spaces.
B. The shamans have a reasonably accurate memory of A'mk sites they learned about as youths.
C. Kaumpta shamans are generally held in high esteem for their traditional knowledge.
D. Modern technologies available to the researchers are likely to be able to find some A'mk sites easily.
E. Most or all A'mk sites are likely to be found within the Kaumpta region.

B

Source: Official Guide 2020

The negated choice A. = The researchers do NOT have reliable evidence that the A'mk of one thousand years ago built important ceremonial spaces.

Why does the negated choice A. not destroy the plan?

If the researchers have no reliable data the the places they want to seek were actually built, then hiring the indigenous people will be of no use!

Please clear this doubts
Thanks