Final answer:
The National Labor Relations Board (NLRB) is responsible for determining the appropriate bargaining unit when an employer and a union cannot reach an agreement on its composition in the union formation process in the United States. Therefore, the correct option is C.
Step-by-step explanation:
If the employer and the union cannot agree on the basis on which employees should be in the bargaining unit, then c. the National Labor Relations Board (NLRB) will determine the "appropriate unit." This is a key step in the union formation process as set by the laws in the United States. When there is a dispute regarding the makeup of the bargaining unit, the NLRB has the authority to make a ruling that will define which employees will be included for the purposes of collective bargaining.
In the process of forming a union, the NLRB plays a crucial role in ensuring protection and fair practice. It is responsible for resolving disputes between employers and unions during the union election process, establishing procedures that firms are obligated to follow.