Why does the industry short-run supply curve slope upward?

What will be an ideal response?

ANSWER:

Disagree. The industry short-run supply curve slopes up because the individual firms’ short-run supply curves slope up. The perfect competitor’s short-run supply curve slopes up because the marginal cost curve slopes up, and the marginal cost curve slopes up because of the law of diminishing marginal product. Hence, the industry short-run supply curve slopes up because of the law of diminishing marginal product.