What's this? It's letter(字母)P. What colour is it? It's green. What's this and what colour is it? It's letter E. It's brown. What's this letter? It's letter N. It's red. P—E—N. Is it“pen”? Yes, it is.

    I have a blue pen in my pencil case(铅笔盒). My pencil case is orange. This is my book. It's my Chinese book. It's in my bag. My bag is black. Look! The bag is on the chair. The chair is yellow. It's my chair. It's nice. I like it.

***90多年来的奋斗历程表明了（   ）

①没有共产党,就没有新中国   

②***是实现中华民族伟大复兴的唯一力量

③只有社会主义才能救中国，只有社会主义才能发展中国

④1921年共产党诞生，我国进入社会主义事业发展新时期     

“DNA是主要的遗传物质”是指（　　）