材料一："平王立，东迁于洛邑，避戎寇。平王之时，周室衰微， 诸侯强并弱，齐、楚、秦、晋始大，政由方伯。"

——《史记•周本纪》

材料二：卫鞅曰：“治世不一道，便国不法古。故汤武不循古而王，夏殷不易礼而亡。反古者不可非，而循礼者不足多。”孝公曰：“善。”以卫鞅为左庶长，卒定变法之令。    

——《史记·商君列传》

阅读材料回答：

从方框中选择适当的单词完成短文。

   What's this on the table? It is a ____  of my new classroom. ____  at the picture. ____  can you see ____  the classroom? I can see a ____  desk in the front of the classroom. Some books are ____  the desk. I can see two white ____ , too. There are____  colored chalks (彩色粉笔n them. ____  is the broom (扫帚)? It’s ____  the door. I like this new classroom.

原鸡每年产卵只有8～12个，而现在的许多产蛋鸡每年可产卵200～300个，这种进化的原因是(      )