Answer:
D.agency shop agreement
Step-by-step explanation:
Agency shop agreement is one where a company or employer is allowed to employ both union and non-union workers. This does not affect existence of the Union.
The employees who are non-union members however need to pay a fee for collective bargaining cost. This fee is called agency fee.
In the given scenario Mary chose not to join the union representing her fellow repair workers, she would still have to pay a fee to the union.
She is part of a agency shop agreement