下列说法正确的是( )

A．25℃时，向饱和AgCl水溶液中加入盐酸，K_sp值变大

B．25℃时，向CaCO₃饱和溶液通入CO₂，有沉淀生成

C．25℃时，AgCl水溶液中，c(Ag^＋)和c(Cl^－)的乘积是一个常数

D．25℃时，在Mg(OH)₂的悬浊液中加入少量的NH₄Cl固体，c(Mg^2＋)增大

When the strike was on,the police were called out to________.[       ]

A. take action  

B. keep guard

C. keep order  

D. watch out