正确改法如下
Yangzi River is longer than ANY OTHER river in China.
Yangzi River is longer than OTHER riverS in China.
大写的词汇是比较容易出在选择题里的
你给的替换是错的,因为你那样改,句子的意思变成了“长江比任何河都要长”,这样说也包含了长江本身.而这在语法里属于improper comparative.