What aspect of system integrations allows different systems to operate as one?

Cohesion in operations is the correct choice because it refers to how different systems work together seamlessly as a unified entity. When systems are cohesive, they can exchange data, share functionality, and operate in concert, thereby enhancing overall performance and usability. This can be achieved through well-defined communication protocols, consistent data formats, and integrated workflows that allow disparate systems to function harmoniously, minimizing friction and maximizing efficiency.

User interface design focuses more on the aesthetic and usability aspects of software applications rather than the functional interoperability between systems. Individual system upgrades can potentially create discrepancies between systems if they are not synchronized, leading to integration challenges. Increased data privacy, while crucial in system design, does not directly relate to how systems operate together. Instead, it emphasizes security measures that protect data rather than promoting integration functionality. Thus, cohesion in operations stands out as the key element that enables different systems to operate as one.