Solution
Option 1 -> Marginal diminishing returns.
Marginal diminishing returns refers to decreasing additional output when one variable input is increased while other inputs remain fixed. This is not about proportional changes in all inputs.
Option 2 -> Decreasing return to scale.
Decreasing returns to scale occurs when output increases by a smaller proportion than the increase in all inputs (e.g., inputs double but output increases by less than double).
Option 3 -> Increasing return to scale.
Increasing returns to scale occurs when output increases by a larger proportion than the increase in all inputs (e.g., inputs double but output more than doubles).
Option 4 -> Constant Return to scale.
Constant returns to scale occurs when output increases by exactly the same proportion as the increase in all inputs (e.g., inputs double and output also doubles).
Hence, Constant Return to scale -> When all inputs are increased by a certain proportion and output increases by exactly the same proportion, this is known as constant returns to scale. For example, if labor and capital both increase by 20%, and output also increases by 20%, the production function exhibits constant returns to scale. This concept is fundamental in production theory and helps firms understand their optimal scale of operations. -> correct