Final answer:
The true statement about turn signals is that you should signal early when turning to alert other drivers and pedestrians of your intention to turn, which is a critical safety practice.
Step-by-step explanation:
The correct statement about turn signals is Signal early when turning. This is because signaling before making a turn ensures that other drivers and pedestrians are aware of your intentions. It is essential for safety and is required by traffic laws. You should not cancel the signal just before making the turn (§1), there is a need to use a turn signal when changing lanes even on a 4-lane highway (§2), and while turn signals can be used to mark your vehicle pulled off to the side of the road for visibility (§4), the primary use is to communicate with other road users your intention to turn or change lanes.