已知函数f(x)=πcos(),如果存在实数x1、x2 , 使得对任意实数x,都有f(x1)≤f(x)≤f(x2),则|x1﹣x2|的最小值是( ) A . 8π B . 4π C . 2π D . π 答案:B — Do you think the weather is good enough for a picnic? — Yes. You couldn't hope for ____ at this time of the year. A. a nice day B. the nice day C. a nicer day D. the nicest day