Which choice most logically completes the text? | Verbal SAT Question

African elephants (Loxodonta africana) communicate using low-frequency acoustic vocalizations known as “rumbles,” which can propagate through savannah environments across several kilometers. Behavioral ecologist Karen McComb and colleagues recorded elephant rumbles and tested how listeners distinguish familiar herd members from unfamiliar conspecifics. While earlier models assumed that low-frequency fundamental tones below 20 Hz (infrasound) carry individual vocal signatures over maximum distances, McComb discovered that acoustic recognition of specific herd members degrades significantly at distances exceeding 1.5 kilometers, because higher-frequency vocal tract resonances (formants) around 115 Hz attenuate and become obscured by ambient environmental noise. McComb therefore concluded that

Which choice most logically completes the text?

elephants can reliably identify individual herd members by rumble alone at any distance within which the rumble remains audible.

long-distance individual recognition by rumble is limited, since the higher-frequency formant cues elephants use to identify specific herd members fade beyond roughly 1.5 kilometers.

infrasound fundamental tones below 20 Hz, rather than formants, are the primary carriers of individual vocal signatures over long distances.

elephant rumbles serve mainly to coordinate group movement over short distances and play no role in social recognition.