Explanation
Correct answer: A.
Choice A is the best answer. Because researchers found “Acasta rocks dating to about 3.75 bya” were similar to “modern rocks formed in a subduction setting,” we can infer that subduction-like processes must have begun occurring in the Acasta Gneiss Complex by this time.
Why the other choices are wrong
Choice B
Choice B is incorrect. We only know about geological processes at the Acasta Gneiss Complex, so we do not have information to make inferences about geological processes in general. Also, notice that the rocks dated to 4.02 bya were found to still be formed in a plume setting, so the transition must have happened after this time.
Choice C
Choice C is incorrect. There’s no mention in the passage of what proportion of the rocks within Acasta Gneiss Complex were formed through subduction, so there’s no basis for this inference.
Choice D
Choice D is incorrect. The passage discusses various rocks in the Acasta Gneiss Complex that are dated to different periods of time, but nothing in the passage suggests that these dates are or were wrong.