A) It occurs when adding more labor always increases output at an increasing rate.
B) It occurs in the short run when at least one input is fixed.
C) It occurs only in the long run when all inputs are variable.
D) It indicates that the marginal cost of production is decreasing.
For Explanation Click Here:
Diminishing returns to labor occur when adding more units of labor to a fixed input (e.g., capital) results in a smaller increase in output. This happens in the short run when at least one input is fixed.