The correct answer is B) High pressure. The steam separator is used to remove moisture from the steam before it reaches the steam whistle. This is important to ensure the whistle operates properly. The steam separator drains to the high-pressure drain system, which is designed to handle the high-pressure condensate from the steam system. The other options are incorrect because: A) Low pressure drain systems are typically used for lower-pressure systems, not the high-pressure steam whistle. C) Contaminated drain systems are used for waste streams, not the steam separator. D) The main turbine is not involved in the steam whistle system.