下表是2012年两个国家的人口统计资料表。据此回答问题。

如图，在正方体ABCD﹣A₁B₁C₁D₁中，点M，N分别是面对角线A₁B与B₁D₁的中点，若$\overrightarrow{DA}$=$\overrightarrow{a}$，$\overrightarrow{DC}$=$\overrightarrow{b}$，$\overrightarrow{D{D}_1}$=$\overrightarrow{c}$，则$\overrightarrow{MN}$=（　　）

已知向量$\overrightarrow{a}=(1,1),\overrightarrow{b}=(2,x)$，若$\overrightarrow{a}+\overrightarrow{b}$与$4\overrightarrow{b}-2\overrightarrow{a}$平行，则实数x的值是（    ）

一 Who helped you clean the classroom yesterday?

— ________. I did it all by myself.

诗歌鉴赏
                                                                                             宿桐庐江寄广陵旧游①
                                                                                                        孟浩然
                                                                                          山暝听猿愁，沧江急夜流。
                                                                                          风鸣两岸叶，月照一孤舟。
                                                                                          建德②非吾土，维扬③忆旧游。
                                                                                          还将两行泪，遥寄海西头④。
注释：①旧游：指故交。②建德：今浙江省建德县一带。③维扬：即扬州。④海西头：指扬州。