问题 填空题

甲醛肟分光光度法测定水中锰时,将显色液倒入50mm比色皿中,于()nm波长处,以()为参比测量吸光度,并做空白校正。

答案

参考答案:450;水

材料题

       “古之人,借食禽兽肉。至于神农,人民众多,禽兽不足,于是神农因天之时,分地之利,制耒耜,教民农作。” 

阅读材料后请回答:

①材料中的“神农氏”是谁,他与谁一起被尊奉为华夏族的祖先? 

                                                                                                                                                           

②材料反映出远古人类的生活方式发生了怎样的变化?

                                                                                                                                                          

③依据材料回答发生这种变化的原因。  

                                                                                                                                                          

④从你所学知识中,指出一处与材料讲述最接近的原始人类遗址。

                                                                                                                                                          

单项选择题