Answer: d. the marginal revenue curve at or above the average variable cost curve
Explanation: short-run supply curve of a firm in a perfectly competitive market describes the relationship between price (P) and quantity supplied (Q). Supply curve in this type of market is a time in which there is an increase in quantity of goods produce by increasing variable factors while fixed factors remain the same.
One major feature of a short run market is that supply of a commodity is kept constant until price becomes greater or equal to average variable cost (AVC), supply is consistent until marginal cost (MC) is equal to average revenue (AVR).