Nancy with her friend _________ now. [ ]
A. play
B. plays
C. is playing
D. are playing
答案:C
为何犯人害怕“三推六问”?
下列检定方法只适合于同型号热电偶的是()方法。
A、同名极法
B、微差法
C、双极法
D、单级法