PCA (Prometheus Certified Associate) sample exam question with answer 195

Question:
Which of the following snippets is NOT a valid component of the Prometheus exposition format?

1. # TYPE node_cpu_seconds_total counter
2. node_cpu_seconds_total{cpu="0",mode="idle"} 177130.24
3. # HELP node_cpu_seconds_total Seconds the CPUs spent in each mode
4. node.cpu.seconds.total.cpu0.modeIdle 177130.24

Answer:
D - correct. Prometheus does not "namespace" metrics using dots. In fact, dots are not valid for use in Prometheus metric names at all
A - this represents the metric type which is a valid component of the Prometheus exposition format
B - this represents a sample
C - this represents the metric help text