下列属于自然区域的是（    ）

阅读下面古诗词，回答相关问题。
                                                                                                          留别王维
                                                                                                           孟浩然
                                                                                               寂寂竟何待，朝朝空自归。
                                                                                               欲寻芳草去，惜与故人违。
                                                                                               当路谁相假，知音世所稀。
                                                                                               只应守寂寞，还掩故园扉。
     【注解】当路，当权者。假，提携。

My cousin is so stubborn ____to change his mind.

给定两个向量$\overrightarrow{a}$=（3，4），$\overrightarrow{b}$=（2，1），若（$\overrightarrow{a}$+x$\overrightarrow{b}$）⊥（$\overrightarrow{a}$﹣$\overrightarrow{b}$），则x的值等于____ ．