阅读理解。

      Deciding to take your family to the Walt Disney World Resort in Orlando, Florida is just the start; there are many decisions(决定) you will need to make and the most important may be when is the best time to go to the Disney World. Every day thousands of people visit the four theme(主题)parks. You'll never find a time when the parks are empty, but you will find that some times of year are better than others for you and your family.

      I think the best time to go to the Disney World is the first two weeks of November. We love this time of year because there are fewer people and the weather is warm enough for shorts(短裤)and swimming but not hot when you visit there!

以下几个实验现象，能说明声音产生的原因的是（　　）

阅读下面这首宋词，完成文后各题。

八声甘州

辛弃疾

    夜读《李广传》，不能寐。因念晁楚老、杨民瞻①约同居山间，戏用李广事，赋以寄之。

    故将军饮罢夜归来，长亭解雕鞍。恨灞陵醉尉，匆匆未识，桃李无言。射虎山横一骑，裂石响惊弦。落魄封侯事，岁晚田间。

    谁向桑麻杜曲，要短衣匹马，移住南山？看风流慷慨，谈笑过残年②。汉开边、功名万里，甚当时、健者也曾闲。纱窗外、斜风细雨，一阵轻寒。

注：①杨民瞻，辛弃疾的友人。②杜甫《曲江三章》其三：“自断此生休问天，杜曲幸有桑麻田，故将移住南山边。短衣匹马随李广，看射猛虎终残年。”