13号、13A型钩尾销孔后壁与钩尾端面间裂纹长度不大于该处厚度的（）时焊修。
A、0.2
B、0.3
C、0.4
D、0.5
参考答案：D
— Why is Mr. Li so happy this morning?
— Because he was honored with a(n) ____ for excellence in teaching.[ ]
A. present
B. gift
C. award
D. reward
直流电动机如何分类？
