已知函数f（x）的定义域为﹣1，5，部分对应值如下表．

f（x）的导函数y=f′（x）的图象如图所示．

下列关于函数f（x）的命题：

①函数y=f（x）是周期函数；

②函数f（x）在0，2是减函数；

③如果当x∈﹣1，t时，f（x）的最大值是2，那么t的最大值为4；

④当1＜a＜2时，函数y=f（x）﹣a有4个零点．

其中真命题的个数是（　　）

根据短文内容, 判断正误。

    When we play a game with our classmates or friends, we usually need to make some rules first. I think it's very important to have rules.

There are lots of rules in my school. We must get to school on time. We have to wear the school uniform on Mondays and Thursdays. We can't run in the hallways. We can't fight. I think it's very good to have rules at school.

    We must follow traffic (交通) rules. We can go at green lights (灯) and have to stop at red lights. The traffic rules make us safe (安全的).  

When we take a car and sit next to the driver, we must wear the safety belts (安全带). Also, children must sit on the safety seats.

根据拼音写出汉字、给划线的字注音。

    建设“幸福德州”，就是让德州人的幸福指数逐渐升高，努力使德州“天更蓝、水更清、路更chànɡ____、房更靓、城更美”。“幸福德州”，幸福在哪里？它藏在老百姓的日子里，绽____放在老百姓的笑脸上。