Each DEU controls the operation of how many MFDs?

Each Display Electronics Unit (DEU) is designed to control the operation of two Multifunction Displays (MFDs). This design allows for efficient distribution of information and redundancy in the aircraft's systems. By having each DEU manage two MFDs, the system ensures that if one MFD fails or experiences issues, the other can continue to operate, providing essential data to the crew. This configuration enhances operational safety and reliability, which are critical components in aviation environments where situational awareness is paramount.

The other options suggest controlling either one, three, or all four MFDs, which does not align with the standard operational structure of the DEUs. Each DEU's focus on two MFDs allows for a balanced workload and systematic representation of flight information without overloading any single unit.