Final answer:
The likely outcome would be that the union would be engaging in an unfair labor practice if it tried to force the school district to keep the administrative assistant position. Option D is correct.
Step-by-step explanation:
The likely outcome of an arbitration proceeding on this matter would be D. The union would be engaging in an unfair labor practice if it tried to force the school district to keep this position. In this case, the school district has made the decision to purchase absence management software, which eliminates the need for an administrative assistant to assign substitute teachers. As the administrative assistant's position is no longer required, the union would be engaging in an unfair labor practice to try to force the school district to retain the position.