她说：“我见过非常昂贵的蛋白质补充剂，它们声称质量上乘，但它们可能不一定对达到平均健康的成年人有好处。”

"I've seen very expensive protein supplements that claim to be high quality but they might not really be beneficial for the average healthy adult," she says.

youdao

这话反过来说就不一定对。

The converse of this statement may not be true.

《新英汉大辞典》

例如，你和疯子打交道时就不一定对。

It is not necessarily true, for example, when you are dealing with lunatics.

youdao

That one's not so obvious. So let's think about this for a second. To sort a list in linear time, would say, I have to look at each element in the list at most a constant number of times.

所以让我们来思考一会,要在线性时间能排序，列表里每个元素最多被使用常数次,不一定是一次，对吧。

麻省理工公开课 - 计算机科学及编程导论课程节选

But for me personally, it doesn't have to be first class.

但是对我个人而言，不一定需要最上乘的。

喜欢巧克力吗？ - SpeakingMax英语口语达人

These kinds of fats are not necessarily bad, and so things like olive oil in the diet tends to be protective and may explain some regional variations in rates of heart disease.

这些脂肪就不一定有害,所以饮食中橄榄油之类的对身体是有益的,这也解释了地域间心脏病发病率的差异

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