用双背齿轮装置供给的的英文

• double back geared

• 用:    40分钟跑完全程 run the course in 4 ...
• 双:    two; twin; both; dual
• 背:    body's back
• 齿轮:    cogwheel; gear wheel wheel-l ...
• 装置:    installation; device; appara ...