若已知行星绕太阳公转的半径为r，公转的周期为T，万有引力恒量为G，则由此可求出（   ）

In America, a friend inviting you to a restaurant doesn't mean that he or she will pay for the meal ______ you are told ahead.

阅读范仲淹的《渔家傲》，完成下面题目。
                                            塞下秋来风景异，衡阳雁去无留意。四面边声连角起。千嶂里，长烟落日孤城闭。   
                                            浊酒一杯家万里，燕然未勒归无计。羌管悠悠霜满地。人不寐，将军白发征夫泪！