题目

George is going to talk about the geography of his country，but I’d rather he________more on its culture. A . foucs B . focused C . would focus D . had focused 答案：B我们规定[]为不超过的最大整数，例如[3.57]=3，[一2.65]=－3，对实数，设()=[]，F()=一[]，给出下列命题：①F()是单调函数；②F()是偶函数；③F()的值域是[0，1]；④F()有周期T=1；⑤F()有反函数F-1()，其中正确的有______________．