The correct answer is D) write up exceptions on the cargo. If you notice that the fruit is beginning to mold while loading it into the reefer spaces, the proper action is to document the issue by writing up exceptions on the cargo. This ensures that the issue is properly recorded, and the receiver of the cargo is aware of the condition. Refusing to carry the cargo (option C) may not be necessary if the molding is caught early and the cargo can still be transported safely. The other options, such as discharging CO2 into the compartment (option A) or carrying the cargo at a cooler temperature than originally planned (option B), are not the correct responses in this situation. The focus should be on properly documenting the issue rather than attempting to mitigate the problem through operational changes.