①个人利益与集体利益在根本上是一致的

②个人利益与集体利益不会发生矛盾

③集体主义要求我们坚持以集体利益为重

④坚持集体主义的同时，个人的正当利益也应得到维护

       Look at the picture. Who is the girl? She is my friend. Her name is Alice Black. She is an English girl.

       Alice has a big family. Her grandparents have two daughters and one son — her father. Alice lives with her grandparents, parents, two brothers and one sister. Alice has two dogs — Bobby and Tony. Bobby is black and Tony is white. Alice likes them very much. Alice is a middle school student. She has a good friend at school. Her name is Helen. They are cousins, too.

我国北方缺水的主要原因是（    ）。