PCA (Prometheus Certified Associate) sample exam question with answer 257

Question:
The metric node_cpu_temp_celcius reports the current temperature of a nodes CPU in celsius. What query will return the average temperature across all CPUs on a per node basis?
The query should return:

{instance="node1"} 23.5 //average temp across all CPUs on node1
{instance="node2"} 33.5 //average temp across all CPUs on node2

Series:

node_cpu_temp_celsius{instance="node1", cpu="0"} 28 
node_cpu_temp_celsius{instance="node1", cpu="1"} 19 
node_cpu_temp_celsius{instance="node2", cpu="0"} 36 
node_cpu_temp_celsius{instance="node2", cpu="1"} 31

1. avg by(instance) (node_cpu_temp_celsius)
2. avg(node_cpu_temp_celsius)
3. avg on(instance) node_cpu_temp_celsius
4. avg_over_time(node_cpu_temp_celsius)

Answer:
A - correct answer