According to the PMBOK® Guide and the PMI Talent Triangle®, leadership is defined as the ability to guide, influence, and direct a team to achieve a goal. It is distinct from management, which focuses on the " known set of expected behaviors " and processes.

Guidance through Influence: Leadership involves the use of interpersonal skills to move a team toward a vision. This often requires discussion, debate, and negotiation to align diverse stakeholders and team members. It is about " guiding " rather than " directing " by command.

Developing Consensus: Effective leadership in a project environment requires the project manager to facilitate communication and collaborate with others to navigate through complex interpersonal dynamics.

Analysis of other options:

Option B: Describes Management. Management is more about maintaining the status quo and using a " known set of expected behaviors " (policies, procedures, and controls) to ensure tasks are completed.

Option C and D: These focus on Technical Project Management and Expert Judgment. While a project manager needs these skills to ensure deliverables are met, they are functional or technical competencies rather than the interpersonal essence of leadership.

As per the PMI Lexicon of Project Management Terms, leadership is a " soft skill " that focuses on the long-term vision and the people involved, utilizing communication and conflict resolution to guide the project to success.