A:毛细血管管壁由一层上皮细胞构成
B:人的红细胞呈两面中央凹陷的圆饼状
C:眼球虹膜位于角膜的后面呈圆盘状
D:大脑皮层有许多凹陷的沟和隆起的回
4×____<37
7×____<59
I have a pencil box. It's blue. There are lots of things in it. I have a pen. It's red and long. I like it. I have three pencils. They are short. I have a ruler. It's big. I have an eraser. It's small.
如果为下列三幅图片反映的历史事件拟定一个主题,最恰当的是