选B
In that=because 连词型词组,表示“在于,因为”.
而c项的because that,在这里,that 是多余的
至于In that和because的区别,两者没有多大的区别
用In that来表示主观的看法,主观的理由等等
because往往表示慎重的逻辑推理,强调因果联系
举个例子：Ice is lighter than water because its structure is different.冰比水轻,因为它的结构不同.
John writes English essays much better than Bob in that John had one-year literature course.约翰写的英语论文要好过鲍勃,因为约翰重修了一年文化课程.