Can you answer this question?

Would you like to observe the stars at the observatory tonight?

The difficulty of this problem makes me scratch my head.

This problem is so difficult to solve, it gives me a headache.

This problem is very difficult.

Her dress was a vivid lemon color, and it stood out.

That proposal is completely unthinkable.

As a practical question, how are we going to fund this project?

He is observing stars at the observatory.

A new approach is needed to solve this set of problems.