What should you do when passing a row of parked cars and you see a driver in one of the vehicles?

Answer: A — Beep your horn to alert the driver

When passing a row of parked cars and you see a driver in one of the vehicles, the appropriate action is to beep your horn to alert the driver. This can help prevent the driver from unexpectedly opening their door or moving into your path, which could lead to a dangerous situation. Using your horn serves as a warning, increasing your visibility to the driver who may not see you approaching. It's important for riders to take proactive measures to ensure their safety, especially in environments where potential hazards are present, such as parked cars that could obstruct visibility or create obstacles. The other options, while they might seem logical in certain contexts, do not prioritize the crucial need to communicate with the parked driver. Speeding up, for example, may create a sense of urgency or panic and does not effectively warn the driver. Leaning to the side might improve your visibility but does not actively signal to the driver that you are nearby. Signaling with your left hand is more relevant for indicating a turn or lane change rather than communicating with a stationary vehicle's driver.