We have looked into this case with our account department， and found they had missed this sum because the accountant who was in

We have looked into this case with our account department， and found they had missed this sum because the accountant who was in charge（）your sum had been seriously ill and stayed in hospital for one month.

正确答案：of

解析:本题考查固定短语 be in charge of 的用法，意思是“负责某项工作”。全句意思是：我们向财务部门调查了此事，结果发现他们漏汇了这笔款项，原因是负责该款项的出纳因病住院一个月。