【单选题】如图为元素X的某粒子的结构示意图,下列说法正确的是( )
【单选题】如图所示的是某圆形反射镜谐振腔的横模图形,则该激光的模式可以用符号表示为( )。
【简答题】在学习化学时我们要善于总结,如我们可以用符号表达式A+B=AB表示化合反应. (1)如果用AB和CD表示两种反应物,则复分解反应发生的符号表达式可表示为______; (2)不是任意两种化合物都能发生复分解反应,必须有一定的条件复分解反应才能发生,这里的条件是______; (3)下表是某同学归纳的复分解反应发生的种类(反应物的类别)的示意图.请你在框内补充某种物质的类别,并用化学方程式举一例满足...
【简答题】(14分)根据下列装置图回答问题(装置图用符号表示): (1)双氧水(H 2 O 2 )是无色液体,可发生如下化学反应: 。反应中MnO 2 的作用是________。在实验室利用此反应制取氧气时,应选用的气体发生装置是________,简述检查本装置气密性的方法:______________________________________________。 (2)KClO 3 在MnO 2 作催...
【单选题】America The Beautiful,is a song almost every American can sing. And while it's true that The Star Spangled Banner has been America's official national anthem since 1931 ,many Americans feel a unique a...
A.
The Star Spangled Banner.
B.
America the Beautiful.
C.
America, America, God mend thy every flaw.
【简答题】阅读理解 Almost every body in America will spend a part of his or her life behind a shopping cart (购物手车) . They will , in a lifetime , push the chrome-plated contraptions many miles. But few will know-...
【简答题】阅读理解 Almost every family in America or England buys at least one copy of a newspaper every day. Some people buy as many as two or three different papers. Why do people read newspapers? Newspapers supp...
【简答题】云南白族的“( )”分别是 一苦、二甜、三回味 。
【单选题】直航船舶对操舵改变航向的快速响应能力称为: