Which is the tool or technique that is used to obtain the list of activities from the work packages?

Data analysis is a general tool category used across many project management processes but is not the specific technique for breaking work packages into activities.

Leads and lags are adjustments applied during the Sequence Activities process to define the timing relationships between activities that have already been identified.

The Precedence Diagramming Method (PDM) is used in the Sequence Activities process to establish logical relationships between activities, not to create the activity list.

Decomposition is the primary tool and technique in the Define Activities process. It involves subdividing work packages identified in the WBS into smaller components called activities or schedule activities, which represent the specific work needed to produce the deliverable associated with each work package.