Which choice most logically completes the text?

|Question 15Verbal

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Exclusively inhabiting tropical countries such as Ghana, wild chimpanzees lack adaptations to seasonal variations in ultraviolet B (UVB) irradiance from sunlight; since UVB exposure enables vertebrates to synthesize vitamin D, Sophie Moittié and colleagues studied zoo chimpanzees in Spain and other mid-latitude countries to see how vitamin D levels are affected by the seasonal variations in UVB irradiance that occur in those locations. They found that chimpanzees' vitamin D levels were significantly lower in autumn than in summer and appeared unaffected by oral supplementation of vitamin D administered by zookeepers. Moittié and colleagues point out, however, that supplementation was rare, highly varied, and poorly tracked, and therefore ____

the effect of supplemental vitamin D on zoo chimpanzees in Spain and other mid-latitude countries can more clearly be observed in summer than in autumn.

the possibility that zoo chimpanzees in Spain and other mid-latitude countries would benefit from supplemental vitamin D during autumn cannot be excluded.

vitamin D levels in zoo chimpanzees in Spain and other mid-latitude countries may be higher during autumn than Moittié and colleagues' data appear to indicate.

differences in vitamin D supplementation likely explain more of the difference in vitamin D levels across zoo chimpanzees in Spain and other mid-latitude countries than seasonal differences in UVB irradiation do.