Final answer:
b) "This fact provides insight into the cultural practices of the Wiradjuri people."
The fact about the art of poisoning flour on Wiradjuri land provides historical insight into the cultural practices of the Wiradjuri people rather than showcasing agricultural advancements or trade practices.
Step-by-step explanation:
Considering the factual evidence that Burney tells us about the "art of poisoning flour" beginning on Wiradjuri land, the impact of this fact is that it provides insight into the cultural practices of the Wiradjuri people. This choice aligns most closely with the historical and cultural context of indigenous practices and their relationship with the environment. The other options do not accurately reflect the content given in the evidence, as they suggest positive skills in agriculture and trade, or induce a subjective horror response which is not informed by the provided material.