Philip buys the pizza shown below: a circular pizza is shown. the center is labeled as point a and a point on the circumference is marked b. what does ab represent?

Its the radius.

A is the point at the centre and B is a point on the circumference.

The distance between the centre and the circumference [ in this case - AB ] is the radius.

Hence, AB is the radius of the circle.

Hi!

So we know it isn't a diameter, because that would be a line that goes across the whole circle, and through the middle.

It could be a radius..
A radius is half of a diameter, with one point in the center of a circle and one point on the circumference.

Yes! It is a radius!

The answer is radius.

Hope this helps! :)