You must read the entire exam problem. I found the snippet above as Problem 5b of the VRS exam of Feb 19, 2020. The problem starts with the following formula which is a disjunction:
![](https://q2a.cs.uni-kl.de/?qa=blob&qa_blobid=12975318277392782057)
In part a), the second disjunction G!b was considered, and in part b), the first disjunct is considered.