According to Standard Methods, a Biochemical Oxygen Demand (BOD5) test requires the sample to be incubated in the dark at what temperature and for how many days?

• 4 °C for 14 days
• 20 ± 1 °C for 5 days
• 35 ± 0.5 °C for 24 hours
• 103 °C for 1 hour