Combinatorics is a branch of mathematics that studies combinations of things.

He passed the bar examination.

His opinion is our litmus test.

There is a mock exam next week.

I have an oral examination tomorrow.

He passed the graduation examination.

We will conduct a practical test of the new product next week.

That remark earned him frowns from those around him.

He bought too much on credit, and his debt increased.

He bought a new car on credit.