问题 单项选择题

变压器(高压电抗器)非电量保护出口继电器动作电压应为直流额定电压的50-65%,以防止当直流()接地时,由于直流回路过大的电容放电引起继电器误动,同时保证直流电压降低时系统的可靠动作;出口继电器动作功率应大于5W,以防止直流系统或回路干扰时发生误动。

A.正极

B.负极

答案

参考答案:A

填空题
阅读理解

三、阅读理解(40分)

Maps are our oldest literature(文献),older than books.People think a map was the first thing the human ever wrote to communicate each other.Perhaps one million years ago,with a stick in the mud of a lake bed,the earlier human drew some lines to stand for a lake,a river,a thick forest and some good hunting grounds beyond the forest.

It made so much sense that people took it for magic(魔术),they expressed the world in a picture.There was something so real about this new thing called "map" that it helped us believe we could get there.It not only strengthened belief that good hunting existed beyond the forest,but it strongly suggested that the future existed;it was a place we could go to and be there tomorrow.What a comfort.On maps all paths lead somewhere.

41.Which of the following statements is true?

A.Maps can't be used to communicate each other.

B.Maps have the same long history as books.

C.No matter how hard you study them,maps don't make any sense.

D.None of the above is true.

42.The earlier human used lines drawn in the mud to express_________.

A.the whole world                              B.real places

C.strong belief                                          D.great comfort

43.Now people regard some lines drawn by the earlier human as _________.

A.the beginning of maps           B.the chanting form of maps

C.real maps                      D.a part of maps

44.It can be concluded that _________.

A.maps are the most useful way of communicating each other

B.the first map showed somewhere far away

C.the first map showed somewhere very near

D.the first map showed all directions