Which of the following speeds is appropriate when a driver lacks a clear view of a railroad crossing?

When approaching a railroad crossing where visibility is limited, maintaining a speed of 15 mph is appropriate as it allows the driver to navigate the area safely while giving them enough time to react to any oncoming trains. At this speed, the driver can efficiently look both ways and effectively respond if a train is approaching, which is critical since trains can come very quickly and may not be easily heard until they are very close. Additionally, this speed reduces the risk of a serious accident while still allowing for forward momentum as the driver assesses the situation. It strikes a balance between ensuring the driver's ability to manage their surroundings and maintaining compliance with safety regulations in potentially hazardous scenarios.