Start with two facts about water. 1) Water has a high specific heat capacity and 2) water has a high heat of vaporization. So you can discard the other two answers.
The specific heat capacity is the amount of heat that a substance need to increase its temperature 1 °C. The bigger the specific heat capacity the more heat is needed to increase the temperature of the substance. Then it is the high specific heat capacity of water what prevents that its temperature increase very rapidly when the sun heats it, which in turn avoids that the water evaporates too fast.
Then, the answer is the high specific heat capacity.
Among the given choices, the only positive effect that may be thought off with the increase in level of CO2 in the atmosphere is the increase of plant growth. Carbon dioxide is an essential compound in the photosynthesis of plants. Therefore, the answer should be letter C.
The answer is C. the exons
