CO₂ Concentrations in the Atmosphere _______ the Past 160,000 Years

Multiple Choice

CO₂ concentrations in the atmosphere _______ the past 160,000 years.

A) have been equal to methane for
B) are higher today than at any time in
C) have followed the opposite trends of temperature for
D) have been relatively constant for
E) have been constant during periods of glaciation over