The gas absorbed by ocean water which can moderate a potential greenhouse effect is:
o2
co2
he2
n2

The gas absorbed by ocean water which can moderate a potential greenhouse effect is CO2 (Carbon Dioxide). 

Answer;

Carbon dioxide

The gas absorbed by ocean water which can moderate a potential greenhouse effect is carbon dioxide.

Explanation;Greenhouse effect is is a process that warms the Earth's surface. This is as a result of radiation and absorption of sun's energy by greenhouse gases. The ocean decrease the rate of accumulation of carbon dioxide in the atmosphere by absorbing carbon dioxide gas which is a green house gas. Oceans absorbs carbon dioxide from the atmosphere where the air meets the water. The turbulence and waves caused by wind makes water to absorb the carbon dioxide.

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.