Consumer surplus is a measure in economics that reflects the difference between what consumers are willing to pay for a good or service versus what they actually do pay. It is essentially the area above the price level and below the demand curve.

Consider the diagram provided:

1. The demand curve is typically represented by the line extending from point P downward.
2. The consumer surplus is the area between the demand curve and the horizontal line representing the price level.
3. Here, point A on the vertical axis represents the price level. The area AB between the price A, the demand curve at P, and the quantity axis at B is the consumer surplus.
4. Therefore, the consumer surplus is the area AB in the given diagram.

Hence, the correct answer is option AB.