多模光纤目前使用的工作窗口是（）
A.0.85μm
B.1.31μm
C.1.33μm
D.1.55μm
参考答案：A
In English class, our teacher often creates an environment _____ we are given the opportunity to solve problems ourselves.
A．when
B．where
C．which
D．that
束细胞
