It's difficult to tell them apart.

很难把他们区分开来。

《牛津词典》

In fact, it was hard for their classmates and teachers to tell them apart sometimes.

事实上，同学和老师有时很难将她们区分开来。

youdao

When scientist Thomas Bouchard Jr. invited the Jim twins to his lab, people there found it very hard to tell them apart.

当科学家小托马斯·布沙尔邀请吉姆双胞胎到他的实验室时，工作人员很难将兄弟俩区分开来。

youdao

It even, I think, identifies the divine and the human, makes them hard to tell apart;binds them, even while we are being confronted with their difference.

我想，甚至这，使圣与人，难以被分辨，把他们联结在一起，尽管我们也看到,圣与灵之不同。

耶鲁公开课 - 现代诗歌课程节选

But nothing blesses those who, like Simon Legree, employ such slaves but can't be bothered to tell them apart.

ECONOMIST: Johnson

And he needed to be able to tell them apart as precisely as possible, to avoid recording two arrivals as one.

ECONOMIST: Small-scale physics

My little brother even raised eight baby possums after their mother was hit by a car (all named Henry, so it was hard to tell them apart).

FORBES: Congress Bites At Pet Exemption