应力的三种形式是______、________、________。
下图是材料拉伸试验的应力-应变曲线图，请标明各点所代表的意义。
材料开始塑性变形所需的应力称为_________。
To decrease foveal fatigue in shade matching，what should you do()
A. 100k for less than 5 minutes
B. wet the tooth
C. place color samples next to tooth
D. match in northern light
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