Concept:Productivity depends mainly on the efficiency and availability of productive resources, with labour as a key factor.
Explanation:Productivity is the ratio of output to input, often written as
InputOutput.
Labour is the most widely used input when measuring productivity in an economy.
The labour force consists of people willing and able to work, making it a primary factor contributing to productivity.
Options A and C affect the labour force indirectly over time, but they are not the direct major factor itself.
Option D is a measure of economic performance, not a factor of production.
Answer:B. The labour force