What ergonomic principle should Mary follow while at her terminal?

Maintaining a straight wrist posture is crucial for preventing repetitive strain injuries and promoting overall comfort while working at a terminal. A straight wrist alignment minimizes unnecessary stress on the wrist joints and tendons, which can decrease the risk of conditions such as tendinitis or carpal tunnel syndrome. This ergonomic principle helps facilitate smoother movements and reduces muscle fatigue, fostering a more efficient working posture.

While the other options may appear to provide guidance on ergonomic practices, they do not emphasize the direct benefits of maintaining wrist posture. Elbows should ideally be kept close to the body and in a relaxed position rather than extended, and a flat keyboard position can sometimes lead to awkward wrist angles, depending on the user's setup. Although wrist supports can provide assistance, they should not be relied upon as the primary solution for maintaining proper wrist posture.