What are the main differences between open-circuit scuba and closed-circuit rebreather systems in diving operations?

What are the main differences between open-circuit scuba and closed-circuit rebreather systems in diving operations?

• A. Open-circuit releases breathed gas; closed-circuit recycles gas with CO2 scrubbing and more complex monitoring; rebreathers require additional training.
• B. Open-circuit recycles gas with CO2 scrubbing; closed-circuit releases breathed gas.
• C. There is no difference in training requirements between the two systems.
• D. Rebreathers are simpler to operate than open-circuit.

Answer: (B)