What color flag must be attached to the extreme end of an extension that overhangs a vehicle by 4 feet or more during the daytime?

Answer: B — Red

A red flag must be attached to the extreme end of an extension that overhangs a vehicle by 4 feet or more during the daytime to ensure safety and visibility. The use of a red flag serves as a warning to other drivers, indicating that there is an object extending from the vehicle, which may pose a hazard. This regulation is established to prevent accidents by making sure that other motorists can easily see the extension. In a roadside or driving environment, a red flag is a universally recognized sign alerting others to an obstruction, hence reinforcing the importance of adhering to safety measures when transporting loads that exceed standard dimensions.