Productivity generally refers to the measure of the efficiency of production. It can be defined as the ratio of outputs (goods and services) to inputs (resources used in the production process). Thus, productivity often relates to "the value of output" relative to the inputs used to generate that output.
In broader terms, productivity can be influenced by factors such as the skills and training of the labor force, technology, and the efficiency of processes used in production. Therefore, while the specific options you provided touch on aspects of productivity, the most comprehensive answer that encapsulates the definition is "the value of output."