it is hard to know

They may be right, but it is hard to know for sure.

It is hard to know what other answer one might come to.

It is hard to know what to do with her.

It is hard to know whether he can even see her.

As for the in between, it is hard to know where to start.

It is hard to know where exactly we should begin.

With so much on offer, it is hard to know what to single out.

It is hard to know exactly the age and number of children who work.

"It is hard to know whether a different president could have been more successful."

It is hard to know where to go, whom to talk to, even what to say.

Well there are so many things wrong with this it is hard to know where to start.

Of course, it is hard to know how often this happens.

It is hard to know exactly what the images are.

It is hard to know how far such enforcement goes.

There are animal studies, but it is hard to know what they mean.

It is hard to know whether you're having a side effect or interaction.

It is hard to know what three lost years have cost Anna.

It is hard to know how to measure this kind of evidence.

Given the small study size it is hard to know if there were in fact any differences.

Yet it is hard to know what he expects to find.

It is hard to know how the war will be solved here.

It is hard to know what to make of such an ambitious project.

But it is hard to know how much one spouse may tell the other about his or her work.

It is hard to know if they are going to devote themselves to the game, he said.

It is hard to know why they did this, but we can speculate.