This is not possible.
Links are grouped by advertiser, and all links for that advertiser need to be approved in one go. This makes things simple and faster to administer.
Why are the links grouped?
If you approve each link individually then the images might end up looking like Swiss cheese. This is because an image can have different links, and if you don't approve some, then you will end up having holes in the image. Grouping them eliminates this problem.