Final answer:
The accident chain refers to the circumstance leading to the accident. It is one of the concepts used to understand how accidents occur.
Step-by-step explanation:
The 'accident' in the accident chain refers to the circumstance that leads to the accident. It is option A - 'The circumstance leading to the accident'. The accident chain is a concept used to understand how accidents occur and is composed of a series of events or factors that contribute to an accident. The accident itself is the result and consequence of these events or factors.
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