Answer:
a. The team needs to verify that the site will appear as expected in as many browsers as possible.
Step-by-step explanation:
Upgrading to HTML5 is a good idea you get a universal experience across a wide spectrum of devices. With HTML5, you get device ubiquity. You get a chance to build something once and have it work across a wide spectrum of browsers.
However, to a non technical person all these steps and coding you have taken to achieve this don't mean anything. They will only be satisfied with what they can observe physically and confirm there are no issues.
This is why option a is most appropriate as opposed to other options. The account manage will need to see and confirm that the site's HTML5 pages are appearing on many browsers as possible without any issue.