An ad must be more than 50% on screen for more than two seconds. This is required for an ad to be counted as a viewable impression.
- An ad must be more than 75% on screen for more than two seconds.
- An ad must be more than 75% on-screen for more than five seconds.
- An ad must be more than 50% on screen for more than two seconds.
- An ad must be more than 50% on screen for more than five seconds.
The correct answer for the above question is:
Here you can read the explanation about the Viewable Ads.