已知二次函数y=x²+bx-4的图象与y轴的交点为C，与x轴正半轴的交点为A，且tan∠ACO=$\frac{1}{4}$.

蓝藻能进行光合作用，原因是      （   ）

情景交际

        A. that's too bad. 

        B I left my cell phone in one of the clothing shops.

        C It doesn't matter.  

        D You should go to the police station.

        E It wasn't there .

        F That's really kind of you. 

M: Why do you look so unhappy , Jane ?

W: I went shopping this morning .____

M: Oh,____ Did you get back ?

W: No, I didn't . I went back to the clothing shop and the shop assistant said that ____. I think someone must have taken it  

M: I think____         

W: I think so, too

M: Well, I can go there with you

W:____ Thanks a lot

M: Not at all . Let's go now

W: OK