PCA (Prometheus Certified Associate) sample exam question with answer 54

Question:
Given the following three time series, which of the following queries CANNOT be used to determine the current value of the up metric for node1 and node2?
Series:

up{job="node", instance="node1"}
up{job="node", instance="node2"}
up{job="node", instance="node3"}

1. up{job="node",instance="node(1|2)"}
2. up{job="node",instance=~"node[12]"}
3. up{job="node",instance=~"node[21]"}
4. up{job="node",instance=~"node1|node2"}

Answer:
A - This query does not yield the desired result because it does not use the regular expression label selector (=~) for the instance label.
Other queries will provide the current value of the up metric for node1 and node2