设函数f(x)的定义域,值域分别为A,B,且A∩B是单元集,下列命题中:
①若A∩B={a},则f(a)=a;
②若B不是单元集,则满足f[f(x)]=f(x)的x值可能不存在;
③若f(x)具有奇偶性,则f(x)可能为偶函数;
④若f(x)不是常数函数,则f(x)不可能为周期函数.
正确命题的序号为____.
为了解全校学生上学的交通方式,该校九年级(8)班的5名同学联合设计了一份调查问卷,对该校部分学生进行了随机调查.按A(骑自行车)、B(乘公交车)、C(步行)、D(乘私家车)、E(其他方式)设置选项,要求被调查同学从中单选.并将调查结果绘制成条形统计图1和扇形统计图2,根据以上信息,解答下列问题:
在下列词语中错别字的下面划横线,再把正确的字写在括号里。任重道远 峰回路转 翻来复去 粼次栉比 松驰下来 面面相觑 走头无路 忍俊不禁 悲天悯人
Rick is a good man.He makes birthday cakes in a shop.His cakes are great and have very good prices,so many people buy his cakes.He makes friends with lots of his customers(顾客).They all like him very much.One evening.he wants to go home,but many of his old customers come in.Rick smiles(微笑)to them,“I am sorry.It is late today.If you need cakes,please come tomorrow.”One of them takes out a nice cake and says to him,“You make so many great cakes for us.This birthday cake is for you.Happy birthday, Rick.”