When Two Companies Merge, the Length-Of-Service Principle of Combining Seniority

When two companies merge, the Length-of-Service Principle of combining seniority lists prescribes that:

A) Employees' length of service is considered regardless of which company they worked for previously; the two lists are combined as one.
B) Employees are given rank positions on the merged lists equal to their rank position on their prior list.
C) Employees of the acquired company are added to the bottom of the list of the acquiring company.
D) Employees are allowed to continue previously earned seniority on separate seniority lists.