If the Earth Were to Warm Up a Bit, What

If the Earth were to warm up a bit, what would happen?

A) Carbonate materials would form in the oceans more rapidly, the atmospheric CO₂ content would decrease, and the greenhouse effect would weaken.
B) There would be a runaway greenhouse effect, with the Earth becoming ever hotter until the oceans evaporated (as may have happened on Venus) .
C) Carbonate materials would form in the oceans more rapidly, the atmospheric CO₂ content would decrease, and the greenhouse effect would strengthen.
D) The ice caps would melt and cool the Earth back to its normal temperature.
E) Carbonate materials would form in the oceans more slowly, the atmospheric CO₂ content would increase, and the greenhouse effect would strengthen.