ZPW-2000轨道电路室外由什么设备构成？
参考答案：
调谐匹配单元、空心线圈、补偿电容器等设备构成。
She searched all the places where she _____ have left her necklace but it was all in vain.
A．might
B．would
C．could
D．should
一个直径是4厘米的半圆形，它的面积是______平方厘米．
