树立以人民为中心的发展思想，必须坚持人民主体地位，将实现好、维护好、发展好最广大人民根本利益作为发展的根本目的。坚持人民主体地位是我国如期实现全面建成小康社会奋斗目标必须遵循的基本原则，这是因为（    ）

①人民群众是社会主义建设和改革的领导力量

②人民群众是真正的英雄、具有无限的创造力

③人民群众根本利益与社会发展规律是统_的

④群众观点是马克思主义哲学首要的基本观点

    Nick was born with no arms or legs. There was only a small foot on his hip(臀部). He can't do the easiest things like washing his face or brushing teeth, but he can type, pick things up between his toes (脚趾)and even kick a ball.

    Nick grew up in Melbourne, Australia. He wasn't happy at school because his classmates often laughed at him. At the age of 10, he even wanted to kill himself. But later, he changed. He tried to look at good things around him. When he was 17, a friend encouraged(鼓励) him to give speeches. From then on, he began to travel around the world and give talk about his life. He thinks it can help others. Up to now, he was been invited to more than 50 countries and given thousands of talks.

    Now Nick is 32 years old. He lives in California with his wife, Kanae, and their 2-year-old son.

    When you are sad, think of him. At least you have arms and legs.

下表是一位母亲给儿子作的成长记录：

根据以上样本数据，她建立了身高 y （cm）与年龄x（周岁）的线性回归方程为$\stackrel{\wedge }{y}$=7.19x+73.93，给出下列结论：

①y与x具有正的线性相关关系；

②回归直线过样本的中心点（42，117.1）；

③儿子10岁时的身高是145.83  cm；

④儿子年龄增加1周岁，身高约增加 7.19 cm.

其中，正确结论的个数是（）