For developing image assets that are effective, which of these is a best practice that should be followed?

Placing the most important content at the center 50% of the image asset
Making it a habit to upload four or more relevant and unique images at the campaign or ad group level
Using images with a white background since these images usually deliver better results
Providing square images exclusively in order to maximize how often assets are able to serve.

The correct answer is:

Making it a habit to upload four or more relevant and unique images at the campaign or ad group level.