阅读短文，从A、B、C、D四个选项中，选出可以填入空白处的正确答案。
    Look at this picture. It is 1 nice classroom. In the picture, you can see a teacher's 2 on his desk. It's a Chinese book. Eight desks and eight chairs in the room. You can see a girl and 3 boys.
    The girl's 4 is Julia. She is eleven. The boy 5 a black hat is Tom. The other boy is Tony. They 6 the same coats and they are the same age. I 7 they are twins. Tom is a 8 boy. A book is in his hand. You 9 see the teacher . 10 is the teacher? He is taking the photo

“自古书契多编以竹简，其用缣（细绢）帛者谓之为纸。缣贵而简重，并不便于人。伦乃造意，用树肤、麻头及敝布、鱼网以为纸。”这主要说明了

将小铁块和小木块放入一盆水中．结果发现木块浮在水面上，铁块沉入水底，就此现象，下列分析正确的是（）