The principal responsibility of managing the dormitory rests

The principal responsibility of managing the dormitory rests with the students _.
A. itself B. of itself C. themselves D. theirselves 为什么选D 并翻译这句话

C.themselves
管理宿舍的主要责任在于学生自己
这里是the students 的同位语,复数,反身代词为themselves
没有theirselves 这个说法