Turbine lubricating oil:

• A. Contaminates the exhaust steam
• B. Must mix well with water
• C. Can be used to operate the turbine governor
• D. Lubricates the labyrinth gland

Answer: (C)

The main idea being tested is that turbine lubricating oil also acts as the hydraulic fluid for the turbine governor. In a steam turbine, the governor uses oil pressure to drive a hydraulic actuator that moves the steam control valves and regulates speed. Because the oil in the lubrication system is circulated under controlled pressure and kept clean, it can reliably transmit the actuation force needed to control the turbine, so it can be used to operate the governor. This makes it the best answer. The other options don’t fit because oil shouldn’t contaminate the exhaust steam, it isn’t meant to mix with water, and lubricating oil isn’t primarily used to lubricate the labyrinth gland.