The correct answer is B) minimize moisture condensation in the boiler gas passages at low loads. An exhaust gas bypass is installed on a waste heat boiler to prevent moisture condensation in the boiler gas passages when the engine is operating at low loads. At low loads, the exhaust gas temperature decreases, which can lead to condensation of water vapor in the boiler. The exhaust gas bypass allows a portion of the hot exhaust gas to bypass the boiler, maintaining higher temperatures and preventing condensation. The other options are incorrect: A) is incorrect because the bypass is not used to improve efficiency at peak loads. C) is incorrect because the bypass is not used to prevent excessive back pressure at high loads. D) is incorrect because the bypass does not recycle exhaust gas to the turbocharger.