You should always signal:

Answer: A — At least 100 feet before you turn

Signaling at least 100 feet before you turn allows drivers behind you enough time to anticipate your movement and react accordingly. Signaling too far in advance, such as at least 500 feet or 1 mile before you turn, can cause confusion or lead to incorrect assumptions about your intended direction. Additionally, signaling too early may also be problematic if there are multiple intersections or turns before the one you intend to make. Waiting to signal within 100 feet of your turn also allows for any last minute adjustments or changes in direction. Signaling at least 5 miles before a turn is excessive and could potentially distract other drivers from paying attention to more immediate traffic situations. Therefore, option A, signaling at least 100 feet before you turn, is the most appropriate and safest choice.