Which tool allows you to blend colors and make transitions between selected areas in an image?

The Gradient tool is designed specifically to create smooth transitions between colors in an image. When using this tool, you can select two or more colors from the Swatches panel and apply a gradient fill that blends these colors seamlessly across a selected area. This is especially useful for adding depth and dimension or creating backgrounds with a polished look, as it allows for control over how colors transition from one to another.

The other tools serve different purposes: the Paint Bucket tool is used for filling an area with a single solid color; the Brush tool can paint with various colors and textures but does not create gradients by itself; and the Clone Stamp tool is intended for duplicating areas of an image without blending colors in a gradient fashion. Therefore, the Gradient tool stands out as the most suitable option for blending colors and making smooth transitions.