滚轮两边各有一个叫做发光二极管的小型电子发光器件。
The wheels have a pair of small electronic light-emitting devices called light—emitting diodes (LED) mounted on either side4.
滚轮两边各有一个叫做发光二极管的小型电子发光器件。
The wheels have a pair of small electronic light-emitting devices called light—emitting diodes (LED) mounted on either side4.
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