Explanation
Correct answer: B.
Choice B is the best answer because it presents a finding that, if true, would support Stöger and her team’s claim that giraffes use humming to communicate when they cannot signal to one another visually. The text indicates that scientists have long thought that giraffes produce little sound and exclusively rely on visual signals to communicate with one another. The text goes on to say, however, that Stöger and her team have recorded giraffes in three European zoos making a low-pitched humming sound, which the team claims the giraffes use to communicate when they cannot see each other. If the giraffes produced these sounds when visual communication was impossible and never produced them otherwise, that would support Stöger and her team’s claim about the circumstance in which giraffes make the sound.
Why the other choices are wrong
Choice A
Choice A is incorrect because finding that giraffes have excellent vision and can see in color would have no bearing on Stöger and her team’s claim that giraffes produce a low-pitched humming noise to communicate when they cannot communicate visually. As presented in the text, Stöger and her team’s claim is restricted to circumstances in which giraffes cannot signal one another visually; if the giraffes are unable to signal visually, their sense of vision is irrelevant to their communication.
Choice C
Choice C is incorrect because finding that wild giraffes have never been recorded making humming noises would not support Stöger and her team’s claim about the function of the humming noise that the researchers recorded from the giraffes in European zoos. The text provides no information about whether researchers have even attempted to record low-pitched humming in wild giraffes, so nothing can be concluded about the implications of the lack of such recordings.
Choice D
Choice D is incorrect because finding that other animals in European zoos had been observed humming would not support Stöger and her team’s claim, since it would not indicate anything about why giraffes produce humming sounds. Different species could produce similar sounds for different purposes, so scientists could not conclude anything about the function of giraffe humming from a finding that some other animals in zoos also hum.