Concept:Productivity is the amount of output produced per unit of input used.Explanation:In a developing economy, labour is the most commonly used input, so productivity is usually measured as output per unit of labour.This is expressed as:Productivity=Quantity of labourTotal outputThis is the output-labour ratio.Capital-output ratio measures capital efficiency, not productivity level.Output growth rate is a change over time, not a measure of productivity.Answer:A. output - labour ratio