Some people are so terribly insincere you can never tell if they are telling the truth.

有些人虚伪得可怕，你绝对无法搞清楚他们是否在讲真话。

《柯林斯英汉双解大词典》

You can never tell what is going to last forever unchanged.

你永远也不能确定什么是永久不变的。

youdao

You can never tell how far emotions will carry a large market move.

你永远都不可能得知情绪能给一个大的市场带来多大的变动。

youdao

Ms. NATALIA BIEGAVISHA (Sales Director, Moscow Bentley Dealership): (Through translator) You can never tell who is going to be a customer.

NPR: Russian Oil Boom Fuels Rise of the Super-Rich

Sandell says you never can tell when you're going to meet a great entrepreneur.

FORBES: Scott Sandell

"We hope forecasts are exaggerating the amount of snow, but you never can tell, " he said.

WSJ: Northeast Braces for Major Blizzard