It's hard to tell who came up with the idea first.

很难说是谁最先提出这个想法的。

The twins look so alike that it's hard to tell them apart.

这对双胞胎看起来如此相似，很难分辨出他们。

It's hard to tell if he's genuinely ill or just a malingerer.

很难判断他是真的生病了还是个装病的人。

The similarity of their voices made it hard to tell them apart.

他们声音的相似性使得很难将他们区分开来。

The sameness in their clothing made it hard to tell them apart.

他们衣服的相同使得很难将他们区分开来。

Her impassive demeanor made it hard to tell what she was thinking.

她的无表情的态度让人很难猜测她在想什么。

The twins semble each other so much that it's hard to tell them apart.

双胞胎看起来像彼此，以至于很难分辨他们。

The twins resemble each other so much that it's hard to tell them apart.

这对双胞胎像得很难分辨。

These wax figures look so lifelike that it's hard to tell they are not real.

这些蜡像看起来栩栩如生，让人难以分辨真假。

The twins resembled each other so closely that it was hard to tell them apart.

这对双胞胎类似于彼此，难以分辨。