According to the PMBOK® Guide, specifically within the Develop Team process of the Project Resource Management knowledge area, teamwork is identified as a critical factor for project success.

Core Objective: The primary goal of the Develop Team process is to improve interpersonal skills, team environment, and overall team performance. The guide explicitly states that project success is heavily dependent on the ability of the project team to work together effectively.

Key Success Factors:

Teamwork is the fundamental glue that allows individuals to operate as a cohesive unit to achieve project objectives.

Effective teamwork reduces communication barriers, increases synergy, and allows for better problem-solving.

It involves building trust, managing conflicts in a constructive manner, and fostering a collaborative culture.

Process Outcomes: Successful development of teamwork leads to improved individual and team competencies, which in turn leads to enhanced project performance and the likelihood of meeting project goals.

Comparison with Other Options:

Team meetings (A): These are tools or communication vehicles, but not a " critical factor for success " in themselves; the quality of interaction (teamwork) within them is what matters.

Subcontracting teams (B): This is a procurement or staffing strategy, not a success factor for internal team development.

Virtual teams (C): This is a specific team structure or technique (using technology to bridge geographical gaps), but the PMBOK® Guide notes that virtual teams often face more challenges in achieving the teamwork required for success.