When referring to the critical rendering path in site performance, a critical resource is:

When referring to the critical rendering path in site performance, a critical resource is:

• any resource that returns 404
• a resource that could block initial display of the page
• any resource that must be loaded
• a resource that takes more than 500ms to load

Correct answer is:

• a resource that could block initial display of the page

Explanation: A critical resource is a resource that could block initial rendering of the page. The fewer of these resources, the less work for the browser, the CPU, and other resources.

Read more here: https://support.google.com/partners/answer/7336426