抗战时期，延安新华电台评论一场战役时说“这是中国军队主动出击日军规模最大的战役，它振奋了中国人民的抗日精神，在国际上引起了极大的反响。”这场战役应该是（　　）

下列说法正确的是（　　）

①NaHCO₃溶液加水稀释，$\frac{c\left(N{a}^{+}\right)}{c\left(HC{O_3}^{-}\right)}$的比值保持增大

②浓度均为0.1mol•L^﹣1的Na₂CO₃、NaHCO₃混合溶液：2c（Na⁺）=3c（CO₃^2﹣）+c（HCO₃^﹣）

③在0.1mol•L^﹣1氨水中滴加0.1mol•L^﹣1盐酸，恰好完全中和时pH=a，则由水电离产生的c（OH）=10^﹣amol•L^﹣1

④已知：K_sp（AgCl）=1.8×l0^﹣10，K_sp（Ag₂Cr₂O₄）=2.0×l0^﹣12，则Ag₂CrO₄的溶解度小于AgCl．

当a∈{﹣1，$\frac{1}{2}$，1，3}时，幂函数y=x^a的图象不可能经过第____ 象限．

B

    One day, Mr. and Mrs. White went shopping by car. They stopped their car near a shop. They bought many things and they wanted to put the things into the car. But Mr. White couldn't open the car. A policeman came to help. Then a man came up and shouted(喊)，“What are you doing? This is my car. ” Mr. and Mrs. White looked at the car's number. It wasn't their car.

如图，已知B是线段AC上的一点，M是线段AB的中点，N是线段AC的中点，P为NA的中点，Q是AM的中点，则MN：PQ等于（      ）