Today's question, answerable in one sentence.

It is midterm week for a lot of you. Rereading feels like studying because the page looks familiar, but familiar is not the same as remembered. The fastest way to find out what you actually know is to close the book and explain it out loud.

What is one concept you were sure you knew until you tried to explain it out loud?

One line is plenty. If you are teaching this week, the same question works on your own course material.