Which choice most logically completes the text?

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Whistler waves are low-frequency plasma waves that on Earth are typically generated by lightning. Numerous recordings of whistler waves on Venus have led many scientists to suggest that the planet's atmosphere is host to extensive amounts of lightning, and, in fact, Venusian whistler waves have similar energy signatures to those of whistler waves generated by lightning on Earth. The majority of Venusian whistler wave data come from two spacecraft missions—the Pioneer Venus Orbiter (PVO) and the Venus Express (VEX)—which have included few observations of other phenomena consistent with lightning occurrences (such as flashes of light), leading other scientists to suggest that ______

there are geophysical characteristics of Venus not shared with Earth that promote the generation of whistler waves.

the purported Venusian whistler waves must actually be some other type of atmospheric activity than whistler waves.

Venusian lightning has properties that make it unlikely to generate whistler waves.

similarities in the energy signatures of Venusian and Earth whistler waves may reflect imprecisions in the PVO and VEX data.