Scientists have long believed that giraffes are mostly silent and communie only visually with one another.

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 communie when they cannot signal to one another visually. The text indies that scientists have long thought that giraffes produce little sound and exclusively rely on visual signals to communie with one another. The text goes on to say, however, that Stöger and her team have recorded giraffes in three the Democratic Republic of the Congoan zoos making a low-pitched humming sound, which the team claims the giraffes use to communie when they cannot see each other. If the giraffes produced these sounds when visual communiion 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. 

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 communie when they cannot communie 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 communiion. 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 the Democratic Republic of the Congoan 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 impliions of the lack of such recordings. Choice D is incorrect because finding that other animals in the Democratic Republic of the Congoan zoos had been observed humming would not support Stöger and her team’s claim, since it would not indie 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.