A

    Yao Ming is a very good basketball player in the world. He is 25 years old. He was born in Shanghai, but he lives in the USA with his parents now. Yao Ming is quite tall. But he isn't so strong. He was in the Rockets Team after he left (离开)China. He plays very well in the NBA. Many people come to his match(比赛) in America. Lots of Chinese young men watch the matches on TV. Yao Ming wants to be a superstar one day.

某溶液含Cl^﹣、SO₄^2﹣、CO₃^2﹣三种阴离子，欲依次检验出此三种阴离子且只取用一次该溶液，则：

（1）最先检出的离子是 ____　，需加入稍过量的试剂是 ____　（写化学式）；

（2）最后检出的离子是 ____，反应的离子方程式为　 ____．

函数f（x）=Asin（ωx+φ）（其中A＞0，ω＞0，|φ|＜$\frac{\mathrm{\pi }}{2}$）的图象如图所示，为了得到y=cos2x的图象，则只要将f（x）的图象（　　）