维氏硬度试样表面粗糙度Ra应不大于()μm。
A.0.4
B.0.8
C.1.6
参考答案:A
氧气的纯度低,金属氧化缓慢,使气割单位长度割件的氧气消耗量()。
—Are you worried about the result of the exam?
—Only________.[ ]
A. absolutely
B. approximately
C. slightly
D. extremely