《穿井得人》的故事告诉我们____（填成语）的危害。

— What's this in English? 

—         a CD.

已知下列方程：（1）2x+3=$\frac{4}{x}$；（2）7x=9；（3）4x﹣2=3x+1；（4）x²+6x+9=0；（5）x=3；（6）x+y=8．其中是一元一次方程的个数是（　　）

用句子补全对话。

Black: Hi, Tom. Long time no see!

Tom:  Hi, Black. ____?

Black: Fine. Thanks for asking.

Tom:  It must be a new shirt you're wearing. ____?

Black: It's made of silk. It's very soft.

Tom:  It looks cool. ____?

Black: 100 Yuan.

Tom:  It's not very expensive. I also want to buy one. ____?

Black: I bought it at Xidan.

Tom:  OK! I like blue best.____?

Black: Yes, there is blue shirt at that store.