By Measuring the CO₂ Concentration in the Vostok Ice Core

By measuring the CO₂ concentration in the Vostok ice core, scientists were able to show that atmospheric CO₂ concentrations fluctuated substantially over the last 160,000 years and periods of low atmospheric CO₂ concentration correspond with

A) warmer interglacial periods.
B) colder ice age periods.
C) years of above average precipitation.
D) years of below average precipitation.
E) both warmer interglacial periods and years of below average precipitation.