Explanation/Reference:
Design Manager in SharePoint 2013 provides a new approach for designing websites. Several new branding and design-based capabilities available in Design Manager enable you to create a compelling look, feel, and behavior for your SharePoint 2013 site. Design Manager also supports importing and exporting a visual design, and can help you ensure a consistent visual experience across all device platforms in your organization.
Incorrect:
Not C: With device channels in SharePoint 2013, you can render a single publishing site in multiple ways by using different designs that target different devices.