有时候是生理特征，有时候不是。

Sometimes they are physical characteristics and sometimes they aren't.

youdao

有时候是，有时候不是。

Sometimes it is and sometimes it isn't.

youdao

真相：有时候是这样的，但是有时候不是。

Reality: Sometimes yes, sometimes no.

youdao

That's because the ideas of physics don't fall into 75-minute segments and sometimes they spill over a little bit.

因为物理的知识不是死板的75分钟课程,所以我会有时候做一些微调

耶鲁公开课 - 基础物理课程节选

When I don't know even necessarily... Well, it's not my choice,

有时候我甚至自己都不一定知道……嗯，这不是我的选择，

有这样的困难 - SpeakingMax英语口语达人

We could also, I think, well, maybe this isn't written out in terms of that convention, which sometimes it's not, so let's also try writing it, such that we have the hydrogen and the oxygen atom there.

我们也可以，我想，好吧，还有可能它不是按照惯例写的，有时候会出现这样的情况，因此，让我们把氢原子和,氧原子成键的情况也写出来。

麻省理工公开课 - 化学原理课程节选