①证明DNA是主要的遗传物质

②确定DNA是染色体的组成成分

③发现DNA如何储存遗传信息

④为DNA复制机制的阐明奠定基础

图示法是我们学习历史的一种好方法，下面能正确反映北宋与少数民族政权并立的示意图是（    ）

① Why not go on Tuesday? It's half price then ____     A. They are Amy's.

② What does your father do? ____     B. I can sing English songs.

③ Are you all right? ____     C. I'd like some tea.

④ How can I get there? ____     D. He is a worker.

⑤ Whose pants are these?____     E. I am l.65 metres.

⑥ How tall are you? ____     F. You can get there by bus.

⑦What can you do? ____     G. Really? Thank you.

⑧ What's the weather like in the USA? ____     H. I feel happy.

⑨ What would you like to drink? ____     I. I'm OK now.

⑩ How do you feel?____       J. It's sunny and hot.

下列句子中没有语病的一项是（     ）

（1）用计算器计算：$\sqrt{11-2}$=____ 　

$\sqrt{1111-22}$=____ 

$\sqrt{111111-222}$=____ 

$\sqrt{11111111-2222}$=____ 

（2）观察题（1）中各式的计算结果，你能发现什么规律？____ 

（3）试运用发现的规律猜想：$\sqrt{1111111111-22222}$=____ ，并通过计算器验证你的猜想．