Which two positions of the master controller are considered running positions?

The correct response identifies series and multiple as the two running positions of the master controller. In the context of train operation, these positions are essential for managing the electrical current supplied to the traction motors, which ultimately affects the speed and performance of the train.

When the master controller is in the series position, it connects multiple traction motors in a way that allows for a higher draw of current, facilitating strong acceleration, especially when starting from a stop. This configuration is particularly useful for heavy trains or steep grades, as it enables better torque management and efficient power delivery to the wheels.

The multiple position allows for the control of multiple traction units or multiple motors in tandem, which also enhances the ability to accelerate and maintain speed under different load conditions. This position is crucial for trains consisting of multiple cars since it provides the flexibility to manage power across several units effectively.

In contrast, the other choices involve configurations like parallel or reverse, which serve different purposes—parallel operates motors in a manner that ensures consistent speed under load but does not provide the initial acceleration benefits of the series, and reverse is used for changing direction rather than forward motion. Understanding the specific functionalities of each running position is critical for effective train operation and safety.