题目

BANANA MILK SHAKE (Enough for two big glasses of banana milk shake) * Two bananas * Two spoons (150g) of ice cream * Fresh milk (125ml) * Chocolate, ice cream and fruitDon't ask your mother for help with this one! It's very easy and it takes several minutes to make it. Put the banana pieces in the blender with the ice cream and the milk. Blend them for about ten seconds(秒). Pour it into the glass. Put some small chocolate and fruit pieces on the top. It's nice and cold with that ice cream in it. Enjoy it.根据以上材料，完成下列句子。每空单词数不限。 （1） We “a＝1”是“函数f(x)＝|x－a|在区间[1，＋∞)上为增函数”的 [　　] A．充分不必要条件 B．必要不充分条件 C．充要条件 D．既不充分也不必要条件