在一个边长为10m的正六边形地面，用边长为50cm的正三角形瓷砖铺满，则需这样的瓷砖____块．

下列说法中符合生活实际的是（  ）

若一个四边形四条边的长分别为a、b、c、d，若a²+b²十c²+d²=2(a c + b d )则这个四边形是(    )

在空格中填上适当的单词，使对话完整正确。一空一词（含缩写词）。

J—Jack D—David

J:Christmas used to be my favorite time of year, but right now I feel terrible.

D:No wonder, Jack. It's our ____ Christmas away from home to study here. A ____ of situation would easily affect people's feelings.

J:What do you  ____ most as Christmas is coming, David?

D:Of course, my family. I spent every Christmas with my family before this year.

J:Me, too.  ____ In the world is better than being with my family at Christmas time. D: At least, your brother is here with you.

J:That's true. Sometimes he can be boring to me, but now, ____ I do feel great to have him ____on this special day here.

D:Maybe he'll be here soon. I hope he will like the gift we bought for him.

J:I'm sure he will. He's always wanted a ____ so that he can record every ____ that moves him deeply here in Beijing, and he can ____ what's recorded with my family.

D:Perfect. In this way, your parents can see people's happy life in Beijing and understand China better. One more thing, our Chinese classmates are going to hold a Christmas party for us, and they want to spend Christmas with us.

J:They are friendly. I'm very glad to get their ____.I will go to the party with you.

①要解决对食品市场监管____________的问题，就必须改革监管体制和工作机制。

②这部小说感人至深，作品主人公的_________，就是著名的民族英雄文天祥。

③学生没打好基础，__________，即不切实际地追求所谓远大目标，难成大事。