通过磁性探伤法、超声波法、电阻法、声发射法等观察零件内部机体的裂纹缺陷。
参考答案：对
黏液血便，右下腹腊肠样包块，应首选的检查是（）
A.B超
B.CT
C.乙状结肠镜检查
D.胃肠钡餐透视
E.灌肠气钡双重造影
An analyst does research about characteristics of market structures. Excess capacity in perfect competition is most likely:（）
A. less than that in monopolistic competition.
B. equal to that in monopolistic competition.
C. greater than that in monopolistic competition.
