According to the PMBOK® Guide, the Develop Schedule process is the process of analyzing activity sequences, durations, resource requirements, and schedule constraints to create the project schedule model. Resource leveling is a specific tool and technique categorized under Resource Optimization.

Resource leveling is a technique in which start and finish dates are adjusted based on resource constraints with the goal of balancing the demand for resources with the available supply.

Scenario: It is used when shared or critical required resources are available only at certain times or in limited quantities, or when they have been over-allocated.

Impact: Unlike resource smoothing, resource leveling can often cause the original critical path to change, usually by increasing the project duration.

A. Three-point estimates: This is a tool and technique used in the Estimate Activity Durations process. While it provides the data used to build a schedule, the act of developing the schedule itself uses those durations as inputs.

C. Precedence diagramming method (PDM): This is a tool and technique used in the Sequence Activities process. PDM is used to create the project schedule network diagram by showing the logical relationships between activities.

D. Bottom-up estimating: This is a tool and technique used in Estimate Activity Resources and Estimate Costs. It involves estimating the components of work and then aggregating them to reach a total.

To build a robust schedule, a Project Manager also uses:

Critical Path Method (CPM): To identify the sequence of activities that represents the longest path.

Schedule Compression: Including Crashing (adding resources) and Fast Tracking (performing activities in parallel).

Leads and Lags: Adjusting the timing between successor and predecessor activities.

What-If Scenario Analysis: Using simulation (like Monte Carlo) to see how different variables affect the deadline.