当隧道长度不大于（）时，隧道内、外的接触线可取同一高度。
A、500m
B、800m
C、1000m
D、1200m
参考答案：C
When she was walking in the street, she met a friend of _______.
A．she
B．her
C．hers
D．her’s
什么是运行级别？Linux有哪些运行级别？
