下列说法不正确的是（ ）
A．氢氧化钡晶体与氯化铵固体的反应是吸热反应
B．氢氧化钾与硝酸的反应是放热反应
C．共价化合物中不可能含有离子键
D．可逆反应达到化学平衡状态时，正、逆反应速率都为0
A、氢氧化钡晶体与氯化铵固体的反应是吸热反应，故A正确；
B、氢氧化钾与硝酸的反应是中和反应，一定是放热反应，故B正确；
C、只含有共价键的化合物是共价化合物，共价化合物中不可能含有离子键，故C正确；
D、化学平衡状态是一个动态平衡，达到平衡时，正逆反应速率相等但是不等于零，故D错误．
故选D．
Having written a book on rock music and a book on jazz music, and now writing a book __31__ the classical music of the 20th century, I felt the __32__ to put somewhere the music that does not quite fit __33__ of these kinds of music. I also felt that I needed to research the beginning of the popular music in Western Europe and the USA in order to __34__ understand the change of the jazz and rock music. I also felt that ethnic music has become so __35__ that one should research the development from Western European and USA music. This book aims at __36__ all these gaps (差异). I did my best to give it a systematic feeling, although it is clear that musicians from such different parts of the world had very __37__ in common. Only after the joining together of the 1907s can we __38__ of a worldwide history of popular music. This book is about the __39__ of that formation (形成). It was not very difficult to decide how to __40__ jazz music from pop music. It was much more __41__ to decide how to separate rock music __42__ the rest of popular music, because rock music has taken in just about everything. Pieces of this book were firstly written for my 2003 books on rock music. __43__ that happened after the 1960s will be in the book on rock music. The __44__ is that you should read this book first, then the __45__ of jazz music and the history of rock music.
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