阅读下面的古诗，回答相关问题。

                                                                                                         【甲】使至塞上·王维
                                                                         单车欲问边，属国过居延。征蓬出汉塞，归雁人胡天。
                                                                         大漠孤烟直，长河落日圆。萧关逢候骑，都护在燕然。
                                                                                                         【乙】出塞·王昌龄
                                                                秦时明月汉时关，万里长征人未还。但使龙城飞将在，不教胡马度阴山。