They could often be called upon to work under fire.

When called upon to answer from my heart, I did.

But why isn't really a question we are called upon to answer.

He would give up his life for me if called upon.

You are being called upon to make an important decision.

We are being called upon to deal with a most serious matter.

I know not who or what she may call upon.

But then, she hadn't been called upon to do this sort of thing often.

It is simply not something Americans have been called upon to do much.

I have not been called upon to do this work.