The correct answer is B because a work package leader is responsible for managing the assigned work package and optimizing the use of resources within that area of responsibility. A work package is a defined portion of project work for which cost, duration, resources, and delivery responsibilities can be estimated and managed. The work package leader coordinates the people, activities, materials, tools, dependencies, and progress needed to complete that package in accordance with the project plan. This role supports the project manager by ensuring that delegated work is executed effectively, reported accurately, and controlled against scope, schedule, cost, and quality expectations. Option A is not the best answer because validation of project deliverables and outcomes normally involves the customer, sponsor, project manager, acceptance authority, or governance body, depending on the acceptance process. Option C is also incorrect because setting the cultural and ethical tone belongs to senior leadership, project governance, sponsor, and project board responsibilities, not to a work package leader as a primary role. PMBOK defines a work package as work at the lowest level of the WBS for which cost and duration are estimated and managed, supporting this answer.

Reference topics: work package leader, resource management, work package control, delegated authority, project organization.