翻译没有人知道为什么恐龙在地球上消失

没有人知道为什么恐龙在地球上消失
可以有多种翻译和表达：
No one knows 【why dinosaurs disappeared from the earth.宾语从句】
Nobody knows 【the reason why/for which dinosaurs died out from the earth.定语从句】
Nobody knows exactly 【the reason for the dinosaurs disappearance/extinction from the earth.介词短语作定语】
No one knows for sure 【the reason why dinosaurs has become extinct on the earth.同位语从句或定语从句】