I owe my education to my parents.

Changes in the social system inevitably occur with time.

Slavery is something that robs human dignity and is absolutely unacceptable.

Feudalism characterized the social system of medieval Europe.

I didn't think he would come.

He thinks that war is a necessary evil.

Do you understand the necessity of this project?

That information is unnecessary.

That information is completely unnecessary.

His thoughts were as we expected.