Identify the wrong statement w.r.t. ${\mathrm{C}}_4$ plants.

The evolution of the C₄ photosynthetic system is probably one of the strategies for maximising the availability of CO₂ while minimising water loss. C₄ plants are twice as efficient as C₃ plants in terms of fixing carbon dioxide (making sugar). However, a C₄ plant loses only half as much water as a C₃ plant for the same amount of CO₂ fixed.