Providing a link to the full site on a mobile web page is a common technique to ensure users can access all content if they find the mobile version limiting.
* Advantages:
* Access to Full Functionality: Users can switch to the desktop version if they need features not available on the mobile site.
* User Control: It gives users the choice to view the site in a layout they are more comfortable with.
* Other Options:
* A. Access to multiple link layers: This does not directly address user needs for full site access.
* B. Targeted site content: While important, it does not replace the need for a full site link.
* D. Navigation links requiring scrolling: This can worsen the user experience on mobile devices.
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Google Developers - Mobile Site Design