What is a common feature of modern fire apparatus related to their main pumps?

Answer: B — priming pump connected to the main fire pump

A common feature of modern fire apparatus is the inclusion of a priming pump connected to the main fire pump. This component is crucial for operation because the main fire pump needs to achieve a vacuum to draw water from a source, such as a hydrant, a static water supply, or a tank. A priming pump facilitates this by removing air from the pump and creating the necessary vacuum, allowing water to flow into the pump efficiently and quickly. The presence of a priming pump enhances the effectiveness and reliability of fire suppression efforts, especially when time is of the essence in emergency situations. By ensuring a rapid and efficient water supply, the priming pump plays a critical role in maintaining the operational readiness of the fire apparatus and supporting firefighters in their critical response efforts.