Please help to answer the following multiple choice question and explain. Thanks.

Question:

When does a production function exhibit decreasing returns to scales?

a) Decreasing returns to scale may happen if there is a fixed factor such as land in the production function, and this fixed factor becomes scarce as the economy grows larger

B. A production function shows decreasing returns to scale if an equal percentage increase in factors of production leads to a smaller percentage increase in output.

C) A production function shows decreasing returns to scale if an equal percentage increase in factors of production leads to a smaller percentage increase in output. This is because factors of production become scare as the economy grows.

D) A production function may show decreasing returns to scale of the costs of inputs increase.

Regards,