D. True. Bats have higher hematocrit level, leading to more oxygen concentrationin the blood. This supplies more oxygen for flying activity.References1. Digestive Adaptations of Aerial Lifestyles. PHYSIOLOGY 30: 69 -78,2015.2. The structural and functional respiratory refinements in birds and bats. The Journal of Experimental Biology 203, 3045-3064 (2000).