The correct answer is: A. Perfect inelastic demand.
Economic rent is the payment to a factor of production in excess of what is necessary to keep it in its current use. It is possible to earn economic rent for a component of production if it has a perfectly inelastic demand. This means that the demand for the component is not affected by changes in price. As a result, the supplier of the component can charge any price they want and still be able to sell all of their output. This will result in the supplier earning economic rent.
Option B is incorrect because a perfectly elastic demand means that the demand for the component is infinitely sensitive to changes in price. As a result, the supplier of the component will be unable to charge any price they want and still be able to sell any of their output. This means that the supplier will not be able to earn economic rent.
Option C is incorrect because a component of production with a non-fixed supply can earn economic rent. This is because the supplier of the component can charge a price that is higher than the minimum price necessary to keep the component in its current use.
Option D is incorrect because a component of production with more than a single use can earn economic rent. This is because the supplier of the component can charge a price that is higher than the minimum price necessary to keep the component in its current use.