Answer: a) Every 1 to 3 months✅
Option: B) Every 6 to 12 months is incorrect because it is too long of an interval for a low-efficiency panel filter ❌
Option: C) Every 3 to 5 years is incorrect because it is too infrequent for a low-efficiency panel filter❌
Option: D) Annually is incorrect because it is also too long of an interval for a low-efficiency panel filter ❌
