题目

高斯函数[x]，也称为取整函数，即[x]表示不超过x的最大整数．例如：[2.3]＝2，[－1.5]＝－2.则下列结论：①[－2.1]＋[1]＝－2；②[x]＋[－x]＝0；③[2.5]＋[－2.5]＝－1；④当-1≤x<1时，[x＋1]＋[－x＋1]的值为2.其中正确的结论有（填序号）． 答案：【1】①③- You can use MSN to talk with your friend on the Internet. -I know. But can you tell me_______?A. what I can use it B. how can I use itC. why can I use it D. when I can use it