The correct answer is option 4: upward sloping to the right.

In economics, the supply curve shows the relationship between the price of a good or service and the quantity supplied by producers. Normally, as the price of a good increases, producers are willing to supply more of it, resulting in an upward sloping supply curve. This is because higher prices create an incentive for producers to increase production and supply more goods to the market.

However, in some cases, there may be certain goods or productive factors that are completely fixed in amount, regardless of the price. This means that no matter how high the price of the good is, the quantity supplied cannot change because there is a fixed limit to the production or availability of the goods or productive factors. In such cases, the supply curve becomes vertical, indicating that the quantity supplied remains constant regardless of the price.

Hence, option 3, which suggests that the supply curve is vertical, is the correct answer.