PCA (Prometheus Certified Associate) sample exam question with answer 2

Question:
Which of the following is an example of a recording rule in Prometheus?

1. ...
     alert: HighMemoryUsage
     expr: node_memory_MemTotal - node_memory_MemFree > 10000000
   ...

2. ...
     alert: CPUUsage
     expr: 100 * (1 - rate(node_cpu{mode="idle"}[5m])) > 80
   ...

3. ...
     record: FreeMemory
     expr: node_memory_MemFree
   ...

4. ...
      record: TotalRequests
      expr: sum(http_requests_total)
   ...

Answer:
Options C and D are correct and represent the recording rule correctly.
Rest two options A and B are example of alert rules.