Which statement about ad extensions isn’t true?
They show additional information about a business
They tend to improve an ad’s visibility
They often appear below the organic search results
They can help improve clickthrough rate
AdWords shows one or more extensions with your ad when it calculates that the extension (or combination of extensions) will improve your performance, and when your Ad Rank is high enough for it to appear. Adding an extension won’t guarantee that it will show with your ad, but you can keep track of when your extensions are appearing on the Ad extensions tab. Since AdWords requires a minimum Ad Rank (factoring in your extensions) before showing extensions, you may need to increase your bid or your ad quality (or both) in order for your extensions to show.
Ad extensions often increase your total number of clicks by improving the clickthrough rate (CTR) of your ads. They provide valuable ways for users to learn more about your business or interact with your ad, such as making a phone call to your business or providing more links to your website.
Read more here: https://support.google.com/adwords/answer/2375499?hl=en