下列结论正确的是（ ）①函数关系是一种确定性关系；②相关关系是一种非确定性关系；③回归分析是对具有函数关系的两个变量进行统计分析的一种方法；④回归分析是对具有相关关系的两个变量进行统计分析的一种常用方法．
A
Linda，14
My mother does most of the housework like cooking and folding the clothes.My father can only do the washing，sweep the floor and take out the rubbish.He really needs to learn how to do the housework.
Celina，13
My mother and my father do 50% of the housework each.My mother does the washing and cleans the living room.My father makes the bed and drives me to school.
Paul，16
My father doesn't do a lot but he tries to help.He hangs__up the clothes after my mother washes them and my mother is happy that he always gives her a hand.
Bill，15
My mother is a doctor.She is busy with her work every day，so she has little time to do the housework.In fact，she isn't good at doing it.So my father has to do most of it.Sometimes my grandmother comes to help.
《关于秦汉农业的若干问题》一文中写道：战国初期，粮食产量每亩只有一石半左右（合今1．0517石），而西汉时，据农学家氾胜之讲，在某些地方“中田亩十三石（合今3．76石），薄田亩十石（合今2．89石）”。这说明（ ）
日本明治维新的成功是多种因素综合作用的结果，其主导因素是( )
商鞅变法和北魏孝文帝改革都是社会转型时期进行的重大改革。相比商鞅变法，北魏孝文帝改革的“除旧布新”主要体现在（ ）
