11.壓力0.5MPa時飽和水的比焓640.1 kJ/Kg，飽和水蒸汽的比焓2748.1 kJ/Kg。若鍋爐壓力為0.5MPa 時水蒸汽的比焓為2452.98 kJ/Kg，則其乾度為： (A)0.66 (B)0.76 (C)0.86 (D)0.96