墨滴入水，扩而散之，徐徐混匀。关于该现象的分析正确的是（         ）（双选，填正确答案标号）

—Our class will have a party      the evening of June 30th. Would you like to come?  —Yes, I'd love to, but I'm going to visit my grandparents in Dalian.

$\cos (\mathrm{\pi }-\mathrm{A})=-\frac{1}{3}$，则cosA的值为(   )

某种冰箱经两次降价后从原来的每台2500元降为每台1600元，求平均每次降价的百分率为____．