焊缝中的光斑之所以难以用超声波探伤发现，是因为其面积较小。
参考答案：错
I work very hard because I don't want to . [ ]
A.let my parents down
B.let down them
C.let my parents to be disappointed
D.let my parents go.
自鼻额缝向两侧横过鼻梁、眶内壁、眶底、颧上颌缝，沿上颌骨侧壁达翼突
A．LeFortⅠ型骨折 B．LeFortⅡ型骨折 C．LeFortⅢ型骨折 D．不对称型骨折 E．纵行骨折
