Question

the intertropical convergence zone (itcz), a band of clouds that encircles earth in the tropics and is a major rainfall source, shifts position in response to temperature variations across earths hemispheres. data from huagapo cave in peru suggest the itcz shifted south during the little ice age (circa 1300 - 1850), but a shift as far into south america as huagapo should have led to dry conditions in central america, which is inconsistent with climate models. to resolve the issue, geologist yemane asmerom and colleagues collected data from yok balum cave in central america and compared them with the huagapo data. they concluded that during the little ice age, the itcz may have expanded northward and southward rather than simply shifted.
which finding from asmerom and colleagues study, if true, would most directly support their conclusion?
a neither the yok balum data nor the huagapo data show significant local variations in temperature during the little ice age.
b both the yok balum data and the huagapo data show increased temperatures and prolonged dry conditions during the little ice age.
c the yok balum data show prolonged dry conditions during the same portions of the little ice age in which the huagapo data show heightened levels of rainfall.
d the yok balum data and the huagapo data show strongly correlated patterns of high rainfall during the little ice age.

Explanation:

Asmerom and colleagues concluded that during the Little Ice Age, the ITCZ may have expanded northward and southward rather than simply shifted. If the Yok Balum data (from Central America) shows prolonged dry conditions (which would be expected if the ITCZ expanded southward, taking rainfall away from Central America) during the same time that the Huagapo data (from Peru, which is south) shows heightened rainfall (expected if the ITCZ expanded southward, bringing more rainfall to Peru), this directly supports the idea of an expansion (as opposed to a simple shift). Option A doesn't support the conclusion as it doesn't show relevant climate - related differences. Option B with increased temperatures is not relevant to the ITCZ shift/expansion conclusion. Option D with correlated high - rainfall patterns would support a shift (if both had similar rainfall changes) rather than an expansion.

Answer:

C. The Yok Balum data show prolonged dry conditions during the same portions of the Little Ice Age in which the Huagapo data show heightened levels of rainfall.