题目

选词填空 snow vacation sit windagain （1） The Smiths go to Hawaii on . （2） Look! There is a dogunder the tree. （3） It often in the north of China in winter. （4） The TV play Home with Kids is veryinteresting, I want to watch it. （5） The trees are shaking! It'soutside. 答案：【1】vacation 【1】sitting 【1】snows 【1】again 【1】windy已知函数 ,则；下面三个命题中，所有真命题的序号是          . ①  函数是偶函数；②  任取一个不为零的有理数，对恒成立；③  存在三个点使得为等边三角形.