A. Equal to zero
B. Less than the saturation vapour pressure over ice
C. Greater than the saturation vapour pressure over ice
D. Equal to the saturation vapour pressure over ice
Saturation vapour pressure increases with rising temperature. Saturation vapour pressure just above liquid water is greater than that over ice. At temperatures below freezing it takes more vapour molecules to saturate air directly above water than it does to saturate air directly above ice.