Answer:
The correct option is B
Step-by-step explanation:
The long run supply curve is a curve which is vertical at the output level which is potential. The potential level of the output is produced by using all the resources which are available in the economy.
And it changes when the labor resource, change in technology or the capital changes. So, decrease in the labor force decreases the labor resources and with that the potential level of output in the economy decreases.