Waec Model Questions Vol1 2021 Biology Question 46

Three desert plants (A, B, C) were studied under identical conditions. Their leaf characteristics are given: - Plant A: leaf area = 50 cm², stomatal density = 200 stomata/mm², cuticle thickness = 5 µm, measured transpiration rate = 0.8 mg/h. - Plant B: leaf area = 40 cm², stomatal density = 150 stomata/mm², cuticle thickness = 8 µm, measured transpiration rate = 0.5 mg/h. - Plant C: leaf area = 60 cm², stomatal density = 250 stomata/mm², cuticle thickness = 3 µm, measured transpiration rate = 1.2 mg/h. Assuming that transpiration rate is directly proportional to stomatal density and inversely proportional to cuticle thickness, which structural adaptation is primarily responsible for the lowest transpiration rate observed among the three plants?