脚手架的拆除作业可以由上而下逐层进行,也可以先拆除连墙件。()
参考答案:对
Part 3
Questions 19-25
If a company wants to evaluate the costs of a training program, the two things it has to know are ______.
A.the training methods used and the staffwho do the training
B.checking on the saving in time regularly
C.examination of the manual work performed
D.evaluation of the management and supervisory training
简述色谱分析的主要特点?