以下____不是进行零件数控加工的前提条件。A.已经返回参考点 B.待加工零件的程序

风险管理中最为重要的环节是（）。

A.风险分析

B.风险估测

C.风险评价

D.选择风险管理技术

—Why didn't you come to my party? I was so disappointed at your absence.

—I'm very sorry.I  _____ but I had a visitor at the last minute.[ ]

A. would like have    

B. would like to    

C. had planned to    

D. were going to

肺与外界进行的气体交换()
血液与组织进行的气体交换()
机体与环境进行的气体交换()

A．呼吸

B．肺通气

C．肺换气

D．外呼吸

E．内呼吸

盛应电动势大小与哪些因素有关？