磁压力式氧分析仪当测量范围在X~100%时,比如测量上限为100%O2,一般选用()作参比气。
A、氮气
B、氢气
C、氧气
D、空气
参考答案:C
It seems to me that the Americans are a highly______people. Most of them like to travel whenever they get the chance.
A.civilized
B.luxury
C.ambitious
D.mobile
维修性是指使产品保持或恢复到规定状态所进行的活动。