药物相互作用是指A．药物在体内的物理化学和药理的配合变化 B．药物在体外的配合变化

      Music is an art that almost everyone enjoys. Everyone can make sounds by singing. All over the world,
many kinds of music developed as people found out how to make sounds in different ways. There are so
many kinds of music to hear that you can soon find a kind that you like. People can get all kinds of feelings
by hearing music. Music can make you march or dance, and it can make you feel happy or sad. 
      More than other arts, music can affect you feelings. This is why music is so popular.
      Every country has its own kind of music and many people like music. But there are also people who
enjoy classical music and pop music. With the help of the recorders and radios, the music is spread all over
 the world, However, there are still great differences between the music of the west and that of the east.
Many of the instruments are very different.