CAP theorem definition taken from Wikipedia:
It is impossible for a distributed computer system to simultaneously provide all three of the following guarantees:
- Consistency (every read receives the most recent write or an error)
- Availability (every request receives a response, without guarantee that it contains the most recent version of the information)
- Partition tolerance (the system continues to operate despite arbitrary partitioning due to network failures)
C and A mean that the system provides these guarantees in the face of partitions. So abandoning these properties during a partition makes the property not hold.
The CA trade-off is only relevant during a partition (because without partitions we can give up P and obtain CA). Then, you need to decide.
The practically relevant choices are CP vs. AP since partitions can always happen.