25℃时，在10mL浓度均为0.1mol•L^﹣1的NaOH和NH₃•H₂O混合溶液中滴加0.1mol•L^﹣1盐酸，下列有关溶液中粒子浓度关系正确的是（　　）

已知$a>0,b>0$，$a+b=2$，则$y=\frac{1}{a}+\frac{4}{b}$的最小值是 （）

Dear Sandy,

    I am very glad to enter my school. I enjoy the life here except for the school lunch. I prefer hamburgers,ice creams and potato chips,but we are not allowed to order them according to the school rules. I usually have little for lunch and I often feel tired and can't follow the teachers in the afternoon classes. What should I do? Do you have any good ideas? Please write to me as soon as possible.

Yours sincerely,

Lucy

注意事项:1）词数90左右，开头和结尾已经写好，不计入总词数;

2）文中不得提及真实的人名、校名等相关信息。

Dear Lucy,

    I am glad to receive your letter.

Yours,

Sandy