Question

2. Which organisms utilize a one-way air flow through their lungs to maximize air flow efficiency and oxygen consumption? A. Amphibians B. Fish C. Mammals D. Birds

Answer 1

The best answer is D, birds.
For more information and details on the way a bird's respiratory system works:
https://asknature.org/strategy/air-flow-patterns-facilitate-efficient-gas-exchange/

Answer 2

The correct answer is option D, that is, birds.  

Birds are the species that uses a one-path air flow via the lungs to enhance the efficiency of air flow and consumption of oxygen. The flow of air in birds plays an essential function at the time of flying. In addition, greater oxygen consumption and airflow efficiency are required by the birds as their heart pumps briskly in order to tackle the flapping of wings that make them fly.