Which of the following key cards is valid on Regional Rail?

The Standard Key Card is valid on Regional Rail as it is specifically designed for personal travel within the SEPTA system, including the Regional Rail lines. This card allows for the purchase and use of passes that are accepted for travel on these services. Such cards typically enable users to tap in and out seamlessly on Regional Rail services, making them a convenient option for daily commuters and occasional travelers alike.

The other cards, such as Corporate or Staff Cards, might be intended for specific organizational or employee purposes and generally do not apply to the broader commuting populace utilizing Regional Rail services. The Guest Card is usually a temporary solution for visitors who may not require the full features of a Standard Key Card or who are looking for short-term travel options. Thus, the Standard Key Card stands out as the proper choice for valid use on Regional Rail.