Efficiency in software refers to:

Efficiency in software specifically relates to the performance of a system during its operation, particularly in terms of resource utilization. This means minimizing CPU and memory usage while the software is running. When a program operates efficiently, it requires less computational power and memory, which can lead to faster execution times and improved overall performance.

This aspect of efficiency is crucial in software engineering, where system resources are often limited or where maximizing performance is essential for user satisfaction and system functionality. By focusing on how well a system uses its resources, developers can create more sustainable and scalable applications that are capable of handling larger workloads and maintaining high-speed processing.

The other options describe different aspects of software but do not capture the core concept of efficiency in the context of resource utilization during operation. Reducing software costs pertains to budgeting and financial planning, development time relates to project management and timelines, while completeness of features concerns the functionality and requirements of the software rather than its operational efficiency.