①A∪B={1，2，3，4，5，6，7}；②A∩B=∅；③A中的元素个数不是A中的元素；④B中的元素个数不是B中的元素．

若集合A含有2个元素，则满足条件的A有____个．

阅读理解

    My name is Sun Liang．Li Feng is my cousin．He is thirteen years old and I'm twelve years old．We study in the same school but not in the same grade．He is in Grade 8 and I'm in Grade 7．

    Li Feng is tall and strong．He plays basketball well．He thinks it's a good way to stay healthy．So he often plays basketball with his classmates in the playground．He likes collecting the pictures of famous basketball players．Last Sunday,he watched a basketball match．He was happy because he saw his favourite basketball star．

    I also like playing sports but music is my favourite．I think it's a good way to relax after a busy day．My father is a music teacher and he is good at playing the piano．So I learn from him to play the piano．It was my birthday yesterday．I had a party and I was happy．

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