复合材料的“损伤-安全”特性,偏轴层的裂纹有60%-90%的裂纹产生在()多少的疲劳寿命以前?
A、10%
B、20%
C、30%
D、40%
参考答案:B
一次函数y=x+4的图象经过P(a,b)和Q(c,d),则a(c-d)-b(c-d)的值为______.
—I was badly ill last Tuesday.
—_______. [ ]
A. It does matter
B. That's good
C. Excuse me
D. I'm sorry to bear that