整句话中文意思是：我希望今天早上发生的那场事故中的每个人不管是谁都平安无事.
首先是选项后面引导一个定语从句而Aanyone,B、none 无法引导定语从句,所以排除,然后剩下是C和D,根据汉语意思是不管是谁,所以选C whoever.
关系代词引导的定语从句举例
关系代词所代替的先行词是人或物的名词或代词,并在句中充当主语、宾语、定语等成分.关系代词在定语从句中作主语时,从句谓语动词的人称和数要和先行词保持一致.
1、who,whom,that
这些词代替的先行词是人的名词或代词,在从句中所起作用如下：
(1) Is he the man who/that wants to see you?他就是想见你的人吗?（who/that在从句中作主语）
(2) He is the man whom/ that I saw yesterday.他就是我昨天见的那个人.（whom/that在从句中作宾语）
2、Whose 用来指人或物,(只用作定语,若指物,它还可以同of which互换）
(1) They rushed over to help the man whose car had broken down.那人车坏了,大家都跑过去帮忙.
(2) Please pass me the book whose (of which) cover is green.请递给我那本绿皮的书.
3、 which,that 它们所代替的先行词是事物的名词或代词,在从句中可作主语、宾语等,例如：
(1) A prosperity which / that had never been seen before appears in the countryside.农村出现了前所未有的繁荣.（which / that在句中作主语）
(2) The package (which / that) you are carrying is about to come unwrapped.你拿的包快散了.(which / that在句中作宾语）