在低压盘、配电箱上的工作，可由一人或多人进行。
参考答案：错
Software Engineering Economy is an effective part of software engineering. Which of the following content is the research content of software engineering economy Ⅰ. Estimation of software development cost Ⅱ. Earn & Cost analysis of software development Ⅲ. Adjustment of software development progress
A．Ⅲ only
B．Ⅱ and Ⅲ
C．Ⅰ and Ⅱ
D．all
B．发生衍射的同时把波源的能量传播到“衍射”区域
C．衍射只有波才能发生
D．只有孔才能发生衍射，一块挡板不可能发生波的衍射
