Which of these devices includes a display screen and software to display graphical representations of pushbuttons and selector switches, which an operator can press to send input signals to a controller?

The correct choice, the Human-Machine Interface (HMI), is designed specifically to facilitate interaction between operators and machines. An HMI includes a display screen that presents graphical representations of control elements like pushbuttons and selector switches. These graphical elements serve as intuitive interfaces through which operators can input commands and receive feedback from the system.

The software within an HMI allows for custom displays that can visually represent the status of various processes, enabling operators to monitor and control machinery more effectively. The ability to interact visually and directly with the system's controls makes HMIs a fundamental component in industrial automation, bridging the gap between human operators and machine functionality.

In contrast, while a SCADA system also provides visualization for process control, it typically functions at a higher level, managing multiple devices and collecting data rather than serving as a primary interface for machine operation. A PLC controller, on the other hand, does not have display capabilities and instead focuses on executing control logic. An embedded control system works closely with specific hardware and software for controlling devices but lacks the interactive graphical interface characteristic of an HMI.

Hence, the HMI stands out as the device specifically designed for operators to interact visually and directly with automated processes, making it the most suitable answer.