钢锭(坯)的皮下气泡或非金属夹杂物，轧制后暴露就形成发裂纹。
参考答案：对
They often praise the policeman _____ his courage.[ ]
A. in
B. on
C. for
D. at
根尖周囊肿最重要的诊断依据是
A．根尖周X线透射区周边有白线围绕B．根管内有浅黄透明囊液C．囊液可见胆固醇结晶D．牙髓无活力E．包括以上各项
