题目

补全对话A:Hi,Dave.Do you know that the Great Wall is the longest wall of the world?B:Yes.And I really admire yourThey were so clever and brave.A:What do you think it was used for?B:It might be used for keeping the wind fromthe sand away.A:Oh,no.There used to be many wars in the north of China.So people built the Great Wall to prevent from entering China.B:Oh,I see.Its was to protect people's safety,wasn't it?A:Yes,you are right.At that time,the leader of China was Qing Shihuang.Thanks to the Great,he got of the wars and joined six countries into a big country.B:He must be the greatest empe小明家照明用的白炽灯泡的灯丝烧断了．他爸爸将断了的灯丝搭在一起后继续使用，发现灯泡比往常更亮，原因是灯丝的（ ）A．电阻变小，电流变大B．电阻变小，电流变小C．电阻变大，电流变大D．电阻变大，电流变小