Final answer:
The provided references do not provide specific information about the principal cause of most accidents. It is important to consult specific sources or statistics for accurate information about the principal causes of accidents in a particular context.
Step-by-step explanation:
The question you asked is not related to the given information in any of the provided references. None of the references provide specific information about the principal cause of accidents.
However, it is important to note that the principal cause of most accidents can vary depending on the context. For example, in car accidents, driver error is often cited as a major cause, while in industrial accidents, failure to follow instructions may be more common. It would be best to consult specific sources or statistics for accurate information about the principal causes of accidents in a particular context.