Option (D) Saturated air is correct. According to the textbook, 'The air containing moisture to its full capacity at a given temperature is said to be saturated.' This means the air has reached its maximum capacity to hold moisture at that particular temperature and cannot absorb any additional water vapour. Options (A), (B), and (C) are incorrect because they refer to different measures of humidity: Relative humidity is the percentage of moisture present compared to full capacity; Absolute humidity is the actual amount of water vapour present per unit volume; Specific humidity is not discussed in the given context.