Rate of transpiration is high in

Answer: Option A

Rate of transpiration is high in C₃ plants.
C₃ plants lose up to 97% of the water taken up through their roots by transpiration. In dry areas, C₃ plants shut their stomata to reduce water loss, but this stops CO₂ from entering the leaves and therefore reduces the concentration of CO₂ in the leaves.
Recent research has shown that many C₃ plant species have significant stomatal openings and transpire water at night even in desert habitats.