PCA (Prometheus Certified Associate) sample exam question with answer 558

Question:
Which of the following queries can be used to get the value of the up metric from exactly one day prior?

1. up offset 1d
2. up[1d]
3. up-1d
4. up offset 86400

Answer:
A - is the correct answer, More at offset-modifier
B - is incorrect as this query gives all values of the up metric between now and one day ago
C - is incorrect as this is not valid PromQL syntax
D - is incorrect as 86400 is not a valid time offset. This answer would be correct if the time offset was instead specified as 86400s