PCA (Prometheus Certified Associate) sample exam question with answer 571

Question:
In a Prometheus alerting rule, what syntax can be used to specify the value yielded by the PromQL expression within an additional alert label or annotation?

1. {{ $expr.value }}
2. {{ $expr }}
3. {{ $value }}
4. $expr.value

Answer:
C - is the correct answer. More at templating
A, D - is incorrect as the proper variable is called value, not expr.value
B - is incorrect as the proper variable is called value, not expr