钢材的焊接性能主要与（）有关。
A.强度
B.塑性
C.含碳量
参考答案：C
计时器事件时间的间隔通过______属性设置。
Seed mixture X is 40 percent ryegrass and 60 percent bluegrass by weight; seed mixture Y is 25 percent ryegrass and 75 percent fescue. If a mixture of X and Y contains 30 percent ryegrass, what percent of the weight of this mixture is X ？（）
A.A
B.B
C.C
D.D
E.E
