Final answer:
The client's description of having a core group of friends who often bike or walk together BEST describes the motivational factor of relatedness.
Step-by-step explanation:
The client's description of having a core group of friends who often bike or walk together BEST describes the motivational factor of relatedness. Relatedness is one of the three basic psychological needs identified by self-determination theory, which refers to the need to establish and maintain close, meaningful connections with others.
Research has shown that having social support and a sense of belonging is crucial for overall well-being and motivation. In this case, the client's core group of friends provides a social environment and a sense of camaraderie, which can enhance their motivation to engage in activities like biking and walking together.