Which adjustment would affect the visibility of a layer beneath another layer in Photoshop?

The selected answer affects the visibility of a layer beneath another layer in Photoshop by controlling the transparency of the layer itself. When you adjust the opacity of a layer, you're determining how much of the underlying layers can be seen through it. A lower opacity value makes the top layer more transparent, allowing more of the layer underneath to become visible. This is a fundamental feature in Photoshop that enables creativity in blending images and designs.

While other options like fill opacity and layer blend modes also influence how layers interact in terms of visibility, the primary and most direct adjustment for governing the visibility of a layer is the general opacity setting. It uniformly affects the entire content of that layer, ensuring a straightforward way to reveal the layers below in a predictable manner.

Adjustment layers serve to alter colors, tones, and other effects but do not directly affect the transparency of the layer they are applied to. Instead, they impact the appearance of layers beneath them through effects and adjustments rather than affecting their opacity directly.