c 定语从句修饰the accident 用which引导 happen是瞬间动词不能直接用happened.不要受hear的影响,此处非hear sb.doing sth
c 特意查了attribute 其中一条目是if people in general attribute a particular statement,painting,piece of music etc to someone,they believe that person said it,painted it etc:
a saying usually attributed to Confucius此言出自孔子,主动语态
本题中：发明出自爱迪生.
c 副词表状态