Which of the following graphs correctly represents the relationship between the pressure and the volume of an ideal gas that is held at constant temperature?

Well, you haven't given us much of a choice of graphs to pick from, have you.

If a sample of an ideal gas is held at constant temperature, then
its pressure and volume are inversely proportional ... the harder
you squeeze it, the smaller the volume gets, and less squeeze
produces more volume.

Actually, the product of (pressure) x (volume) is always the
same number.

The graph of that relationship is all in the first quadrant.
It starts out very high right next to the y-axis, then drops down
toward the x-axis while curving to the right and becoming horizontal,
and ends up trying to get closer and closer to the x-axis but never
actually becoming zero. 

Liquid. good luck : )