Auxiliary boilers supply steam for all services except which of the following?

Auxiliary boilers are specifically designed to provide steam for various shipboard systems, including heating systems, freshwater generation, and powering pumps. However, they do not supply steam for main propulsion. The primary steam used for propulsion on a ship typically comes from the main boilers, which are designed to handle the high pressures and temperatures required for driving the propulsion turbines.

Thus, the main propulsion system operates independently from auxiliary boilers, relying instead on the main boiler's steam generation, which is tailored for the demanding requirements of propulsion rather than the general services provided by auxiliary boilers. This differentiation in function highlights why the correct answer pertains to the main propulsion service, as it is outside the scope of what auxiliary boilers are designed to support.