PCA (Prometheus Certified Associate) sample exam question with answer 415

Question:
How many uniquely-named series are generated by a histogram metric type and what form does it/do they take?

1. 3, <basename>_bucket, <basename>_sum, and <basename>_count
2. 1, <basename>
3. 1, <basename>_bucket
4. 3, <basename>_sum, <basename>_count, and <basename>{quantile="<φ>"}

Answer:
A - is the correct answer
B - is incorrect as histogram metrics generate three uniquely named series using the base metric name and applying the following three suffixes: _bucket, _sum and _count
C - is incorrect as a histogram metrics also generate <basename>_sum and <basename>_count series
D - is incorrect as these are the uniquely-named series generated by a summary metric type