In which situations is a flight crew member prohibited from consuming alcohol according to the FARs?

According to the Federal Aviation Regulations (FARs), flight crew members are prohibited from consuming alcohol within 8 hours of drinking, which is often referred to as the "bottle to throttle" rule. This regulation is in place to ensure that pilots and other crew members are free from the effects of alcohol during their duties, ensuring the safety and well-being of passengers and crew.

The 8-hour rule is critical because alcohol can impair judgment and reaction times, which are vital for safe operation of an aircraft. By enforcing this time frame, the regulations help to minimize the risk of alcohol-related incidents during flight operations.

The other options relate to different aspects of alcohol consumption and its effects on performance, but they do not capture the specific prohibition defined in the FARs. Therefore, the 8-hour guideline is the most relevant and direct rule that flight crew members must adhere to.