One of the Major Differences Between Earth and Its Neighboring

One of the major differences between Earth and its neighboring planets Venus and Mars is the lack of large quantities of CO₂ in its atmosphere. If all three planets were originally formed with significant quantities of this gas in their atmospheres, where is the majority of this CO₂ on Earth at the present time?

A) dissociated by UV and visible sunlight into carbon and oxygen that now exists in abundance as separate chemicals
B) concentrated high in the atmosphere where it contributes to the greenhouse effect
C) dissolved in seawater, a situation that cannot arise on the neighboring planets
D) locked up in carbonate and carbon-rich rocks and minerals formed in the sea and on Earth's surface