Every company uses the same style guide or design system to ensure the web is consistent.

A style guide is a higher level design system that integrates code snippets.

Style guides and design systems are shared libraries that define things like color, typography, and how buttons are used. 

All of the above.

You can find all the inconsistencies in a site, many of which you may not have considered.

You can determine which aspects of the site need more attention.

It's a good way to help convince stakeholders, clients, and collaborators that the team should create a design system.

All of the above.

It's a good way to align team members around a common problem. When you see the problems for yourself, they become more meaningful as to why they need to be fixed, and how.

Interface inventories are extremely time consuming and often take a month or two to complete.

Interface inventories should always be outsourced to experts.

All of the above.