新鲜水果用保鲜薄膜包裹或放入冰箱冷藏室可延长存放时间，主要是因为包裹或冷藏后可以（ ）
A：不让水分散失
B：杀死内部的细菌
C：减少水果果皮损伤
D：抑制呼吸作用
They were playing volleyball on the beach when it began to rain ____ (sudden).
— There is milk in the fridge. Please buy some on your way home.
— All right.
若ab＝1，x＝ 11+a+11+b ，y＝ a1+a+b1+b ，则xy＝____。
下列离子组在指定溶液中能大量共存的是（ ）
