Correct Answer: Vertical
  

Solution : The correct answer is (a) Vertical.

The vertical aggregate supply curve in the long run indicates that the level of output is determined by factors such as technology, the quantity and quality of resources, and institutional factors, rather than the price level. In the long run, all input prices, including wages and other production costs, are assumed to be flexible and fully adjustable.

In the long run, while changes in the price level may affect the distribution of income and wealth, they do not impact the overall level of output. Therefore, the long-run aggregate supply curve is represented as vertical, indicating that the economy produces at its potential output level regardless of the price level.