add information about pull_request.opened

Author: hectorsector

responses/07.0_add-trigger.md

@@ -4,10 +4,10 @@ Great! Your learner now has information about what they're expected to do in thi
 Every step in a course will be triggered by a GitHub Event. All possible events are documented in [Events Types & Payloads on the GitHub Developer Guide](https://developer.github.com/v3/activity/events/types/).
 
 ## Step 8: Add an event
-Let's now find the `event` that will trigger the step. Because we want the learner to open a new Pull Request, the event we're looking for is `pull_request.opened`.
+Let's now find the `event` that will trigger the step. Because we want the learner to open a new Pull Request, the event we're looking for is [`pull_request`](https://developer.github.com/v3/activity/events/types/#pullrequestevent). Whenever this event occurs, information about the pull request is delivered to Learning Lab. However, if we just write `pull_request`, _any_ interaction with a pull request will cause this step to be triggered. We're specifically looking for the learner to _open a pull request_. We can filter the event to only opened pull requests by using `pull_request.opened` instead.
 
 ### :keyboard: Add an event
-1. Add an `event` for the first step
+1. Add a `pull_request.opened` event for the first step
     - Note: You can do this by editing the file, or accepting my suggested change
 
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