Final answer:
The least effective posture for support agents in nonverbal communication is 'd. Fold arms,' as it suggests a closed or defensive attitude which can hinder open and supportive interactions with users.
Step-by-step explanation:
In the context of nonverbal behaviors for support agents, posture can significantly affect communication with users. An effective support interaction depends not only on what is said but also on nonverbal cues. Of the options provided, d. Fold arms is considered the least effective posture for support agents. Folding one's arms can be perceived as a defensive or closed posture, which may imply disinterest, standoffishness, or resistance. This can create a barrier to open communication and may make the user feel uncomfortable or undervalued.
In contrast, an open stance, facing the user, and establishing eye contact are nonverbal indicators of engagement and willingness to assist. These postures signal active listening and a readiness to engage in a helpful dialogue, thereby promoting a positive interaction.