Transparency
Keyboard: TRANSPARENCY
Turns transparency on or off for the selected image. When transparency is on for an image, entities located under the image are visible for images that support alpha transparency, that is, images that have at least one color that can be viewed as a transparent color.
Select image(s): Select one or more images.
On/<Off>: To show entities located under the selected images, choose On. To hide entities located under the selected images, choose On.