Which step of planning process involves other managerial functions as well and leads to 'doing what is required'?

The correct option is Implementing the plan.

Detailed Explanation:
Planning is the primary function of management, laying down the blueprint for future actions. The planning process consists of several sequential steps, beginning with the formulation of objectives and ending with monitoring the execution. Among these steps, implementing the plan is the crucial stage where plans are translated into concrete action—essentially, "doing what is required."

This step stands out because it is the point where the planning function connects directly with other key managerial functions:
1. Organizing: In order to put the plan into action, resources must be assembled, work must be structured, and authority relationships must be established.
2. Directing: Managers must guide, supervise, motivate, and communicate with employees to ensure they perform the tasks required to execute the plan.
3. Staffing: The right people must be placed in the right positions to carry out the operational tasks defined by the plan.

While the earlier steps in the planning process (such as setting objectives, developing premises, and selecting an alternative) are purely analytical and decision-making exercises, implementation is action-oriented and requires coordination across the entire management spectrum to achieve the desired goals.