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重点讲解：
1. wear down (使)磨平；(使)磨光；
The machines start to wear down, they don't make as many nuts and bolts as they used to.
机器开始出现磨损，螺母和螺钉的产量不如从前了。
2. even though 即使；尽管；纵然；
She never took a taxi, even though she could afford to.
尽管她坐得起出租汽车，但她从未坐过。
3. pick up 拿起；提起；拾起；捡起；
She bent down to pick up her glove.
她俯身去捡手套。
4. go extinct 灭绝；绝种；
Most animals went extinct because of evolution.
大部分动物的绝迹是因为进化演变之故。
n. 发源地，来源，原始资料
