PCA (Prometheus Certified Associate) sample exam question with answer 88

Question:
Let job="node" represent a Node Exporter scrape.
Which of the following queries gives the duration in seconds of the last scrape for each of the instances in the node job only?

1. scrape_duration_seconds{job="node"}
2. scrape_duration_seconds
3. last_scrape_duration_seconds{job="node"}
4. last_scrape_duration{job="node"}

Answer:
A - the proper metric to use is scrape_duration_seconds with label. Check Automatically generated labels and time series