During holidays，Kitty usually goes to see the exhibits in many museums，such as the history museum，the art museum，the museum of science and technology and the museum of natural history．There are thousands of wonderful things in museum.There are paintings，sculptures(雕塑)，costumes(服饰)，swords(剑)，ancient animal bones and plants，stuffed animals(动物标本)and many others．It is always a good review of history to visit those museums．It is also a great way to learn more things by myself．

①表明他已经进入了青春期 ②表明他已经进入了成年期 ③是正常的，是成长过程中必然出现的现象 ④是身体不够健康的表现