Suppose that co2 in the atmosphere was held at a constant, natural level for a few thousand years. then, co2 was added to double the atmospheric level rapidly, and this new, doubled level was maintained for a few thousand years.

what was the most likely change in the typical average temperature of the planet?

temperature before the increase in CO2 was a few degrees lower than temperature after the increase.

Explanation:

CO2 in the atmosphere has the property of trapping heat by absorbing it. So, with increase in the level of CO2 in the atmosphere the more heat will be absorbed by it and hence the temperature before the increase in CO2 was a few degrees lower than temperature after the increase.

Level of CO2 ∝ Temperature of the Earth

the answer is c i believe