Answer:
A. Both concepts explain why marginal cost increases after some point but diminishing marginal returns applies only in the short run when there is at least one fixed factor, while diseconomies of scale applies in the long run when all factors are variable.
Step-by-step explanation:
Diminishing marginal returns explains the outcome of increasing input in a short run by keeping one production variable constant, this variable could be labour or capital.
The law of diminishing marginal return states that when there is additional unit in any of the factors of productions and others are kept constant, there will be an initial decrease in incremental output per unit.
Economies of scale explains the effect of that will occur when variables inputs are increased in production on a long run, it explains the difference in increased total input against increase in output.