Final answer:
In GIMP, you cannot directly create adjustment layers as you would in Photoshop; instead, you duplicate the layer (Ctrl + Shift + D) and then apply adjustments to this new layer. The provided keyboard shortcuts are incorrect for creating an 'adjustment layer' in GIMP.
Step-by-step explanation:
The question is asking about how to create an adjustment layer from selected content in GIMP, which is a free and open-source image editor. None of the listed keyboard shortcuts will specifically create an 'adjustment layer' as adjustment layers are a feature of Adobe Photoshop, not GIMP.
However, in the context of GIMP, to perform image adjustments on a separate layer, you would typically duplicate the current layer and apply your desired changes to that duplicate. The closest equivalent to an adjustment layer in GIMP, would be to duplicate the layer using the keyboard shortcut Ctrl + Shift + D, then applying changes to this duplicate. The options provided in the question (A, C, D) do not correspond to this action, and option B (Ctrl + Shift + N) is incorrect as it creates a new layer without duplicating the content of the selected layer.