一根弹性长绳沿x轴放置,左端点位于坐标原点,A点和B点分别是绳上x1=2m、x2=5m处的质点.用手握住绳的左端,当t=0时使手开始沿y轴做简谐振动,在t=0.5s时,绳上形成如图所示的波形.下列说法中正确的是( )
A:此列波的波长为1m,波速为4m/s
B:此列波为横波,左端点开始时先向上运动
C:当t=2.5s时,质点B开始振动
D:在t=3.5s后,A,B两点的振动情况总相同
阅读理解
A
We all know that Taiwan is considered as the Treasure Island of China. It is very beautiful. Recently we have been closely connected. Several months ago, a group of 19 Taiwanese children flew to Chengdu in order to begin a tour to study pandas. The middle school children were from Chiayi County in southwest Taiwan and were chosen because of their excellent performances at school. During the visit, the children saw pandas up close. They were very excited to see so many pandas at the same time. The children also traveled to the Mount E'mei scenic area and met local school children. At last, they said, “The pandas are very cute, and we are all happy.” They also said the children in Chengdu were very friendly to them, and they all liked there. They hoped to visit Sichuan again.
民族团结、国家统一是我国历史发展的主流。阅读下列材料,回答问题。
材料一 下图是某老师所绘的《唐蕃关系示意图》:
材料二 元朝的统一给各族人民相互交往和学习提供了有利的环境。蒙古等族人民成批迁往内地,汉族人也大量来到边疆,契丹、女真等族人民早已进入黄河流域,各族人民杂居相处,互通婚姻,逐渐融合。当时,许多阿拉伯人、波斯人迁入中国,同畏兀儿、蒙、汉等民族逐步融合,形成一个新的民族——回族。
材料三 17世纪,漠西蒙古准噶尔部的噶尔丹勾结沙俄,大搞分裂,发动叛乱。康熙帝三次率军亲征,大败噶尔丹。18世纪,回部首领大、小和卓发动叛乱,乾隆帝派兵平息。接着,清朝设置伊犁将军,管辖整个新疆地区。
下面语段中划线字的拼音正确的一项是( )
在一片“森林”中,我们倦怠精神为那力争上流的白杨所振奋;我们怅惘缺憾的人生为那怀着悲悯之心的果树所充实;我们为老树的引颈受戮而感叹,为悬崖边的树与命运抗争的姿态所折服。生活在树的荫庇下,我们无忧无虑,因为有绿的滋润;我们感谢祝福,因为有鸟语花香和新鲜的空气