I spent a lot of time on this question even though it appears relatively easy. I didn't like A but ended up picking it by eliminating others.
Choice A asks "why do Kayapo use video technology to create legal records". The passage answers the question "why do kayapo use video technology in transactions with government" but not the question in choice-A.
The question of "why do kayapo use video technology in government transactions" is different than A. The passage only says that Kayapo use video in government transactions to create legally binding records. But it doesn't say why they use video in government transaction to create legally binding records.
Is the reason A is correct only because of the word "binding" in the passage?