Which choice most logically completes the text?

|Question 15Verbal

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Exclusively inhabiting tropical countries such as Senegal, 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 Italy 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 winter 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 they caution against concluding that ____

vitamin D levels among zoo chimpanzees in Italy and other mid-latitude countries likely show different seasonal patterns than do vitamin D levels among wild chimpanzees in Senegal and other tropical countries.

the lack of an observed effect of supplemental vitamin D on zoo chimpanzees in Italy and other mid-latitude countries may reflect shortcomings in the data rather than actual ineffectiveness.

providing zoo chimpanzees in Italy and other mid-latitude countries with supplemental vitamin D has no promise as a strategy for offsetting winter reductions in their vitamin D levels.

winter reductions in UVB irradiance in Italy and other mid-latitude countries can contribute to variations in zoo chimpanzees' vitamin D levels.