In Adobe Workfront, the initial project setting used to identify and report on key tasks is the Milestone Path. Adobe documentation explains that milestones can be associated with tasks to indicate important steps in the life of a project, and that the collection of predefined milestones is called a milestone path. Workfront also states that milestone paths allow key tasks in a project to be associated with predefined milestones, giving managers and stakeholders a high-level view of project progress. In practice, the project owner applies a milestone path to the project first, then associates individual key tasks with milestones from that path. This supports milestone reporting and milestone views across projects. Schedule controls working and non-working time for date calculations, while Resource Leveling Mode relates to resolving resource allocation conflicts. Neither setting is designed to mark key tasks for milestone reporting. Therefore, the correct answer is A. Milestone Path.