美国1787年宪法最具创新性的内容是(    )

以下是一位同学在研究性学习中搜集的一组图片。分析这组图片你认为该同学探究的主题是（    ）

在植物界中能产生种子并用种子繁殖的植物类群称为____，人们根据它们种子外层有无____包被，又将它们分为被子植物和裸子植物两类．

短文改错。假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。每处错误涉及一个单词的增加、删除和修改。

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1.每处错误及其修改均仅限一词；2.只允许修改10处，多者（从第11处起）不计分。

    The winter holiday is coming. My classmates and I are talking about how to do during the holiday. We can chose between staying at home and take a trip. If we stay at home, it is comfortable but there is no need to spend money. But in that case, we will learn little about world. If we go on a trip abroad, we can broaden your view and gain knowledges we cannot get from books. Some classmates suggest we can go to places of interest nearby. I thought that it is a good idea. It does not cost many, yet we can still learn a lot.