观察以下等式：

sin²30°+cos²60°+sin30°cos60°=$\frac{3}{4}$，

sin²20°+cos²50°+sin20°cos50°=$\frac{3}{4}$，

sin²15°+cos²45°+sin15°cos45°=$\frac{3}{4}$，…

分析上述各式的共同特点，判断下列结论中正确的个数是

（1）sin²α+cos²β+sinαcosβ=$\frac{3}{4}$

（2）sin²（θ﹣30°）+cos²θ+sin（θ﹣30°）cosθ=$\frac{3}{4}$

（3）sin²（α﹣15°）+cos²（α+15°）+sin（α﹣15°）cos（α+15°）=$\frac{3}{4}$

（4）sin²α+cos²（α+30°）+sinαcos（α+30°）=$\frac{3}{4}$（　　）

某同学取用生石灰时，发现装满生石灰的塑料试剂瓶已经膨胀破裂，为此他所在的小组同学进行了如下探究：

【提出问题】该生石灰是否变质？其主要成分是什么？

从方框中选择最佳选项完成对话，有两项多余

a. Why does she like singing?

b. She likes sports, singing and dancing.

c. When and where was she born?

d. She was a good student in the college.

e. Why does she become famous?

f. How old was she when she was in college?

g. That's right.

A: Who is your favourite singer?

B: Li Yuchun.

A:____ 

B: She was born in 1984 in Chengdu, Sichuan.

A: So she is twenty-eight years old now.

B:____ 

A: Do you know where she studied?

B: Yes. She studied at Sichuan Music College.____ 

A: Do you know what her hobbies are?

B: Sure.____ 

A: I know many young people like her. ____ 

B: Well, I think that's because she sings well.