Which factor does NOT affect blood alcohol concentration?

Answer: B — Time of day when alcohol is consumed

The factor that does not affect blood alcohol concentration (BAC) is the time of day when alcohol is consumed. BAC is primarily influenced by how much alcohol is ingested, the individual's body weight, and the rate at which their body metabolizes alcohol. When a person consumes alcohol, the amount ingested directly affects how much is present in their bloodstream. Heavier individuals typically have a higher blood volume, which can dilute alcohol more effectively, leading to a lower BAC compared to lighter individuals consuming the same amount. Additionally, the rate of metabolism plays a crucial role. Different individuals metabolize alcohol at different rates, which can influence how quickly alcohol is processed and cleared from the body. Time of day does not have a direct physiological impact on BAC. While factors like fatigue or alcohol tolerance may change due to the time, they do not alter the actual concentration of alcohol in the blood at a given moment post-consumption.