Question

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
which choice most logically completes the text?
a. 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.
b. the possibility that zoo chimpanzees in spain and other mid - latitude countries would benefit from supplemental vitamin d during autumn cannot be excluded.
c. 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.
d. 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.

Explanation:

The text discusses the study of vitamin D levels in zoo chimpanzees in Spain and other mid - latitude countries. It mentions that vitamin D administration was rare and variable, and the researchers found that vitamin D levels were affected by seasonal variations in UVB irradiance. Option D is correct because the text states that "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". This implies that the data on supplementation (colleagues' data) can indicate the reasons for vitamin D level differences.

• Option A: The text does not say that the effect of supplemental vitamin D is more clearly observed in summer than autumn. It focuses on the role of supplementation in explaining differences rather than seasonal observation clarity.
• Option B: The text is about explaining differences in vitamin D levels, not about the possibility of benefit from supplementation.
• Option C: The text does not suggest that vitamin D levels in zoo chimpanzees in mid - latitude countries cannot be excluded. It is more about the factors (supplementation vs UVB) affecting the levels.

Answer:

D. 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.