What Best Describes How Carbon Dioxide Concentrations in the Atmosphere

What best describes how carbon dioxide concentrations in the atmosphere have changed in the last 500 years?

A) Concentrations were mostly steady until ~1850 when they began to increase.
B) Concentrations increased until ~1850 when they began to decrease.
C) Concentrations decreased until ~1850 when they began to increase.
D) Concentrations varied wildly until ~1850 when they became more constant.
E) Concentrations have remained constant throughout history.