①ax²+bx+c=0；②3（x﹣9）²﹣（x+1）²=1；③x+3= $\frac{1}{x}$ ；④（a²+1）x²﹣a=0；⑤ $\sqrt{x+1}$ =x﹣1，

其中一元二次方程的个数是（   ）

加拿大学者哈罗德·伊尼斯在《传播的偏向》中这样评价梭伦：“他相信，违背公正必然要扰乱公众的生活。个人对自己的行为负责。于是，权威的根基就被摧毁了。”梭伦改革时，“权威的根基就被摧毁了”主要得益于（    ）

    It is on Sunday．My friends and I will go to the bookshop．I like reading____．It is interesting．Sue likes reading____books．Sam doesn't like reading books．He wants to buy a ____．So his subjects are very good．My grandparents like reading____every day．But my parents like reading____．They often read them in the evening．