The correct option is Use the types keyword and list the specific activity names you want to allow.

GitHub Actions lets you narrow an event to specific activity types using the types key under that event. To meet the requirement you configure the workflow so that it listens to the pull_request event and then you list only opened and reopened under the types key. Set the on key to pull_request and under pull_request add the types list with opened and reopened so the workflow runs only when a pull request is opened or reopened and it ignores other activities such as synchronize or edited.

Use the on keyword with a conditional expression that checks github.event.action is incorrect because an if condition controls jobs or steps after the workflow has already been triggered. It does not define which activity types are allowed to trigger the workflow in the first place, which is what the types key does.

Use the events keyword with a regular expression that matches event names is incorrect because there is no events key in the workflow syntax and regular expressions are not used to filter activity types. You filter activities with the types list under the specific event.

Use the workflow keyword with a list of event names to include is incorrect because there is no workflow key for event subscriptions. Triggers are defined with the on key and activity filtering is done with the types key.

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