（Ⅰ）求f（t）的单调减区间；

（Ⅱ）求证：f（t）+f（t+2）+f（t+4）是定值．

根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。

     I had a wonderful time with my exchangeprogram(交流活动中心) in France. It's much 1 than I thought. I felt a little nervous before I reached France, but there wasn't any reason to be so. My host 2 is really nice.

     They managed various ways to make me 3 at home. Every day I 4 practicing 5 French, I wouldn't believe how 6 progress I 7 in French! Although I still make some mistakes, I can think something in French without

    8  everything into Chinese like I used to. My biggest challenge is learning how to behave at dinner table. All the things are really different 9 the way they are at home. You are not supposed to eat anything with your hands except bread. Another thing is that 10 is very rude to say “I'm full now.” you should say “It is delicious." instead.