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.

①皮肤②胃黏膜③神经细胞④蚯蚓⑤细胞内蛋白质等化合物⑥病毒⑦同一片草地上的所有山羊⑧一池塘中的所有鱼类⑨一片森林⑩一池塘中的所有生物

正比例函数y=kx（k≠0）的函数值y随x的增大而减小，则一次函数y=kx﹣k的图象大致是（　　）

计算：
（1）$\frac{-3a}{b}·\frac{a{b}^2}{-a^3{b}^2}÷\left(-\frac{6b}{a^2}\right)$；
（2）$\frac{a-2}{a-1}-\frac{4a-5}{a-1}$