Answer:
The correct answer is option A.
Step-by-step explanation:
It was J.M Keynes who gave the concept of inelastic and vertical long run aggregate supply curve.
The classical economists believed that the supply curve will be upward sloping all the time.
It was Keynes who stated that in the long run, the output will not increase with the increase in price.
The long run supply curve will shift with the changes in factors of production.
The aggregate supply curve will also be vertical at full employment level, because if all the resources are employed, the output level can not be increased, despite increase in price.