Sentence examples for hard problem from inspiring English sources

This is the hard problem.

This is a hard problem.

It was a hard problem then.

"It is a very hard problem".

Is cancer just an impossibly hard problem?

Now that is the really hard problem.

These are hard problems.

There are also no easy answers to hard problems.

"When people realised these were hard problems, there was retrenchment.

Allegedly, however, there are "hard problems" they will never overcome.

Here's where the hard problems arise.