质点仅在恒力F的作用下，由O点运动到A点的轨迹如图所示，在A点时速度的方向与x轴平行，则恒力F的方向可能沿（　　）

我国境内目前已确定的最早人类距今（  ）       

As you research music, you will find much that is familiar to you. You will find music which tells you interesting places and exciting things to do. You will find music which expresses that are often own.
Music is an expression(表达) of the people. As you research, you will find music of people at work or at play. You will find expresses love of the country, love of nature and love of home. Music is also an expression of the composer(创作者). The composer expresses his own music ideas. He studies the materials(材料) of music and discovers of using them. He looks for new kinds of musical expression.
Music can suggest actions and feelings which we share(分享). We can enjoy playing and singing music, dancing and listening to the music of the people and the composers of different times and places.