设N_A表示阿伏加德罗常数的值。下列说法正确的是 [ ]

A．1mol乙醛中含C-H键的数目为3N_A

B．1 L浓度为1 mol/L的醋酸钠溶液中含有N_A个CH₃COO^-

C．某温度时，1L pH＝6的纯水 中含有1.0×10^－6N_A个H⁺

D．电解饱和食盐水，当阴极产生2.24L H₂时，转移的电子数一定为0.2N_A

What happened to the city after the mass move

A．Housing costs decreased.

B．Crime rate was much lower than before.

C．All business moved out.

D．Cities declined.