Productivity as Output per Worker

Steps:

• Define productivity: It measures output relative to inputs, like workers or hours.
• Evaluate each option: Check if it shows more output per unit of input.
• Identify increase: Look for explicit rise in output per worker or similar metric.
• Confirm proof: Only clear per-input gains prove true productivity growth.

Why B is correct:

• Productivity is defined as output per worker; B directly shows this rising from 3 to 4 tractors per month.

Why the others are wrong:

• A: Equal percentage increase in workers and output means no change in output per worker.
• C: More workers can boost total output without improving efficiency per worker.
• D: Night shift adds total production but doesn't specify if it's due to more input or better efficiency.

Final answer: B