重点讲解：
1. be based on 以…为基础；
例句：Early musicwas based onsingle tunes,or melodies.
早期的乐曲是以单一的曲调或旋律为基础的。
2. be made up of 由…组成；
例句：The airis made up ofa mixture of gases.
空气是由多种气体组合而成的。
3. let's say 比如说；比方说；
例句：Another example, you want to be an artist,let's saya painter, but you can't seem to find time to lift a paintbrush.
再比如你想成为艺术家，比方说画家，但是你好像总是没时间拿起画笔。
4. build up （使）积聚；（使）逐渐增加；
例句：We have continued tobuild upour capabilities.
我们在持续不断地加强我们的能力。
5. there's no way 没有可能；
例句：There wasabsolutelyno waythat we were going to be able to retrieve it.
我们绝对不可能把它找回来。
