Geographers were once concerned largely with exploring areas

Geographers were once concerned largely with exploring areas unknow to them and (from) describing distinctive features of individual places.
为什么括号中的错 怎么改
答：with
They were concerned with doing A and with doing B.
有人认为去掉from,我觉得不妥.因为 1.既然是改错题,说明这个词不合适.2.因为doing A短语太长,有必要再重复一下这个with.3.为了避免误以为它与were连用.