How do you unlock the background layer in Photoshop?

The process of unlocking the background layer in Photoshop involves double-clicking on the layer in the Layers panel. When you do this, Photoshop automatically converts the background layer into a regular layer, allowing you to freely edit it. This means you can apply transformations, adjustments, and effects that are not permitted on locked background layers, making this method very intuitive and straightforward for users.

The other options represent different actions that don't directly accomplish the goal of unlocking a background layer. For instance, right-clicking and selecting "Unlock" isn't an option available in Photoshop; there is no such feature to unlock. Using the "Layer > New > Layer from Background" menu option does allow for creating a new layer, but it requires navigating menus rather than the more direct method of double-clicking. Merging the layer with another does not unlock it either; it combines the two layers and changes the layer structure fundamentally without unlocking the original background layer. Hence, double-clicking is the most efficient and user-friendly method for unlocking a background layer in Photoshop.