问题 单项选择题

逆变器的频率精度应不大于().

A.±2%

B.±1%

C.3%

D.2%

答案

参考答案:A

问答题

根据建国以来我国人口与耕地变化情况分析回答:

 

(1)建国以来我国人口数量呈现什么特点?我国人均耕地变化又有什么特点?

                                                                                                                                                                

(2)我国人口与耕地关系中,存在着怎样突出的问题?产生这一问题的主要原因是什么?

                                                                                                                                                               

                                                                                                                                                                

(3)为了解决上述问题,我国的基本国策是什么?

                                                                                                                                                                

                                                                                                                                                               

判断题