PCA (Prometheus Certified Associate) sample exam question with answer 216

Question:
Which of the following queries contains a range selector?

1. sum(up) / count(up)
2. histogram_quantile(0.5, http_request_duration_seconds_bucket)
3. avg(up)
4. delta(node_mem_MemAvailable_bytes[1h])

Answer:
D - is the correct answer. In this query, [1h] is the range selector, range vector selectors