问题 单项选择题

老顶初次垮落步距与其岩石性质及距地表垂深有关,一般在()米。

A.20~50

B.10~20

C.5~10

D.50~70

答案

参考答案:A

问答题

       请你说出三次科技革命发生的年代及各自的标志性成果。第三次科技革命时,中国社会处于什么状态?是否受益,为什么?试结合我国目前的现状,谈谈你的认识。

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                              

                                                                                                                                                              

单项选择题