我们的四肢上，凡是能够弯曲或转动的部位一定都存在有 [ ]

A．神经系统

B．肌肉

C．关节

D．能量

The factory has _____ workers due to the drop in sales, which will lead to an increase in unemployment.

A．paid off

B．laid off

C．set off

D．put off