If Company X considered a good year to be any year in which earnings were at least 20 percent of sales, how many of the years shown were good years?
A. None
B. 1
C. 2
D. 3
E. 4
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如图所示,在R,L,C元件串联电路中,施加正弦电压u,当XC>XL时,电压u与i的相位关系应是μ()。
A. 超前于i
B. 滞后于i
C. 与i反相
D. 与i同相
What percent of the sample voted for at least one of the two winners?
A. 11%
B. 20%
C. 55%
D. 61%
E. 90%
如图所示,已知平面图形的形心为C,面积为A,对z轴的惯性矩为Iz。则图形对z1轴的惯性矩为()。
A. Iz+Ab2
B. Iz+A(a+b)2
C. Iz+A(a2-b2)
D. Iz+A(b2-a2)
某简支梁AB受荷载如图(a)、(b)、(c)所示,今分别用F(a)、F(b)、F(c)表示三种情况下支座B的约束力,则它们之间的关系应为()。
A. F(a)<F(b)F(c)
B. F(a)>F(b)=F(c)
C. F(a)=F(b)>F?
D. F(a)=F(b)<F?