利用等离子切割钢管时,将割炬滚轮接触钢管,喷嘴离钢管表面之间合适距离为()。
A、1~2mm
B、30~50mm
C、10~20mm
D、3~5mm
参考答案:D
-- Have you moved into your new house?
-- Not yet. The rooms _______.
A.are painting
B.have been painted
C.are being painted
D.have painted
一般化学试剂的规格()。
A.优级纯
B.分析纯
C.化学纯
D.实验试剂