Use the following statements to answer this question: I. We cannot measure the returns to scale for a fixed-proportion production function.
II) Production functions with inputs that are perfect substitutes always exhibit constant returns to scale.

A) I and II are true.
B) I is true and II is false.
C) II is true and I is false.
D) I and II are false.

Fixed-Proportion

A production process in which the inputs are used in fixed ratios, with no substitution possible between them.

Perfect Substitutes

Goods or services that can be used in exactly the same way, where the consumer is indifferent between the two and will choose the cheaper one.

Scale

The size, extent, or level of something, typically used in the context of production or operations to indicate magnitude or capacity.