下面的算式中，先算减法的是（  ）。

“我做过一个梦，梦见杂交水稻的茎秆像高粱一样高，穗子像扫帚一样大，稻谷像葡萄一样结得一串串，我和我的助手们一块儿在稻田里散步，在水稻下面乘凉。”袁隆平曾经这样描述过自己的梦想。对此认识错误的是（    ）

已知四边形ABCD是正方形

（1）如图1．点M在边BA的延长线上，点N在边BC上，且AM=CN，连接MN，DM，DN，判断△DMN的形状（直接写出答案）．

（2）如图2，当店N在边AB上，点N在边BC的延长线上，AM=CN，连接MN，取线段MN的中点G，连接DG，DM，判断线段DG和线段MG的关系并说明理由．

（3）如图3，当点M在边AB的延长线上，点N在边BC的延长线上，AM=CN，连接MN，DM，DN，点G是线段MN的中点，连接BG，DG，连接GC并延长交BD于点H，若∠AMN=75°，判断线段GH和线段BD的关系并说明理由．

根据短文内容，选择正确答案。

    Mike had a nice blue cup which he liked best. It was a present from his aunt for his fifteenth birthday last year. He cleaned it once a day and took good care of it. His cat, Mimi, was very naughty(淘气的) and sometimes it could make some trouble(麻烦) for Mike.

    The day before yesterday, the cup was broken(打破) by his cat. He felt unhappy. Susan saw him and asked, "You look sad. What's the matter with you?"

    Mike said, "There is something wrong with my cup."

    Susan said, "Don't worry. I can repair it."

    Mike felt surprised and asked, "Repair? You can repair it? You?"

    "Yes. Believe me! Where is it?" Susan answered.

     "Here. My cup is broken. Are you sure you can repair it?" Mike took out his broken cup.

     "Ha……, I made a mistake(错误). I think your__1__ is broken," Susan said.

    Hearing what Susan said, Mike couldn't help laughing.