【判断题】It is polite to wear jeans and slippers while visting.
【简答题】若信号数学表达式中的独立变量取值是连续的,则称为 ,若独立变量取离散值,则称为 。
【单选题】酒店工作中迎接客人时,微笑传递出( )信息。
【判断题】It is polite to finish everything on your plate.
【判断题】It is polite to point at someone with chopsticks.
【判断题】Nowadays, it is polite to refer to African Americans as the negros.
【简答题】函数 中自变量x的取值范围是 ;若分式 的值为0,则x= .