问题 选择题
日本东部海域9.0级大地震所引发的福岛核电站泄漏事故,让全世界都陷入了恐慌。下面有关核辐射的相关知识,说法正确的是(   )
A.核泄漏中放射性物质都是天然放射性元素

B.放射性辐射对人类都是有害的

C.α、β、γ三种射线中只有γ射线是不带电的

D.可以通过改变放射性物质的外部环境来改变放射性衰变的快慢

答案

答案:C

问答题

在鸦片战争以后,中国社会性质发生了重大的变化。请结合课本知识回答下列问题:

中国社会性质发生了怎样的变化?哪些条约的签订体现了这一变化?  

                                                                                                                                                            

                                                                                                                                                            

                                                                                                                                                            

在这一变化过程中,中国人民进行了哪些奋斗和抗争?给我们什么启示?

                                                                                                                                                            

                                                                                                                                                            

                                                                                                                                                            

                                                                                                                                                            

                                                                                                                                                            

                                                                                                                                                            

单项选择题