Answer : 2. "Uniform Resource Locator"
Explanation :

1. The full form of URL is Uniform Resource Locator. A uniform resource locator, colloquially called a web address.

2. In normal text ads, you define the display URL yourself: If your website address begins with a subdomain (for example, "support" in "support.google.com"), your display URL May include that subdomain.

3. In expanded text ads, your display URL is a combination of your website's domain (and, where applicable, subdomains) and the text in your “Path” field.