Explanation
Correct answer: D.
Choice D is the best answer because it most logically completes the text’s discussion of whistler waves on Venus and the question of their origin. The text explains that whistler waves are plasma waves and that on Earth they are generated by lightning. The text goes on to state that numerous recordings of whistler waves on Venus have led many scientists to suggest Venus hosts lightning. However, the text goes on to explain that data from the PVO and VEX missions have included little evidence of the other phenomena that would be expected if lightning were occurring in Venus’s atmosphere. Because there is a lack of additional evidence of lightning, it is reasonable to conclude that some scientists would be skeptical that lightning is the source of the whistler waves on Venus and would suggest unique geophysical characteristics of Venus as an alternative explanation for the waves’ generation.
Why the other choices are wrong
Choice A
Choice A is incorrect because the text indicates that the other scientists are responding to the PVO and VEX data simply not showing additional evidence of lightning on Venus, not to flaws in the data. The text presents the similar energy signatures of Venusian and Earth whistler waves as an established observation and doesn’t suggest the PVO and VEX data are imprecise.
Choice B
Choice B is incorrect because the text presents the similar energy signatures of Venusian and Earth whistler waves as an established observation. The text indicates that the other scientists are concerned with the lack of corroborating evidence of lightning on Venus, suggesting not that they doubt that the waves are whistler waves but rather that they doubt that the waves are generated by lightning.
Choice C
Choice C is incorrect because the text indicates that the other scientists are responding to the data providing little corroborating evidence of lightning on Venus. This suggests that instead of making a suggestion about properties of Venusian lightning, the other scientists likely would suggest that there may not even be lightning on Venus.