The company is implementing XenDesktop globally for desktop virtualization. How should the architect recommend installment of controllers for high availability?

Installing three Delivery Controllers in each datacenter provides robust local high availability and redundancy, ensuring that if one or even two controllers fail in a datacenter, the remaining controller(s) can continue to manage user sessions and broker connections, fulfilling the global high availability requirement. This setup prevents single points of failure within each site and supports the distributed nature of a global deployment.

This option specifies three controllers in specific locations but does not explicitly state "in each datacenter" nor imply global coverage if there are more datacenters.

This option, similar to B, specifies three controllers in specific locations without ensuring coverage for *each* datacenter globally.

This option provides an uneven distribution of controllers, with only one controller in London, which introduces a single point of failure in that specific datacenter, undermining high availability.