低合金高强度钢和碳钢的碳当量______时,焊接性优良。
A.小于0.70%
B.小于0.60%
C.小于0.50%
D.小于0.400%
参考答案:D
Poverty depresses most people, but in ________ case of my father it was otherwise
A./
B.a
C.the
D.one
概念模型一般用图纸表达,主要用于()
A.分析和比较
B.规划管理
C.规划实施
D.效果表达