The first step to optimize the critical rendering path is:

By WPExpert Guides Last updated Jun 17, 2020

analyze and characterize your critical path: number of resources, bytes, length.
optimize the number of critical bytes to reduce the download time (number of roundtrips)
minimize number of critical resources: eliminate them, defer their download, mark them as async, and so on
optimize the order in which the remaining critical resources are loaded: download all critical assets as early as possible to shorten the critical path length.

Correct answer is:

analyze and characterize your critical path: number of resources, bytes, length.

Explanation: The general sequence of steps to optimize the critical rendering path is:

Analyze and characterize your critical path: number of resources, bytes, length.
Minimize number of critical resources: eliminate them, defer their download, mark them as async, and so on.
Optimize the number of critical bytes to reduce the download time (number of roundtrips).
Optimize the order in which the remaining critical resources are loaded: download all critical assets as early as possible to shorten the critical path length.