To the Degree That the Plumbers and Steamfitters Union Conducts

To the degree that the Plumbers and Steamfitters union conducts costly training and apprentice requirements for prospective electricians, it is

A) shifting the supply of plumbers to the left.
B) shifting the supply of plumbers to the right.
C) shifting the demand for plumbers to the left.
D) kinking the supply of plumbers to make it vertical at the level of the constraint.