Fatigue()
A. occurs under cyclic loading
B. is unaffected by sharp angles in a material
C. only occurs in resin composites
D. all of the above
铸锭用发热剂的主要作用是防止钢锭产生()。
A. 冒涨
B. 裂纹
C. 夹杂
D. 缩孔
直流电抗器用于限制短路电流和()。
A. 稳定电压
B. 稳定电流
C. 稳定电器
D. 稳定电弧
When a liquid wets a solid completely，the contact angle between the liquid and the solid is()
A. 0°
B. 45°
C. 90°
D. 135°
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