如果句子为：China is a country with a long history one, I think,__ is becoming stronger.答案为which, 引导非限制定语从句.I think 为插入语.
倘若句子为：China is a country with a long history. One, I think,__ is becoming stronger.其答案为that, I think 依然为插入语, that is becoming stronger为one 的同位语.