Which contributing factor would apply for a vehicle that hydroplanes and strikes a guardrail?

Hydroplaning occurs when a vehicle’s tires lose contact with the road surface due to a layer of water, which can lead to a loss of control. During such conditions, the speed of the vehicle significantly affects the likelihood of hydroplaning. The term "unsafe speed" specifically refers to driving too fast for the current road conditions, which can include wet or slippery surfaces.

In this scenario, if a vehicle hydroplanes and subsequently strikes a guardrail, it indicates that the driver was operating the vehicle at a speed that exceeded what was safe given the presence of water on the road. Therefore, "unsafe speed" aptly describes the situation as it encompasses the concept that the driver did not adjust their speed to accommodate for the road conditions, thereby contributing to the incident.

Other options like driver distraction, speeding, or following too closely might influence driver safety and vehicle control in different contexts, but they do not specifically address the condition of hydroplaning in relation to the control over the vehicle on a wet surface. "Unsafe speed" directly correlates with the adjustment needed in response to adverse weather conditions, making it the most relevant contributing factor in this case.