Final answer:
The correct answer is 200 feet; it is unsafe to make a u-turn when oncoming vehicles are closer than this distance. This rule ensures both the safety of the driver attempting the u-turn and that of other road users.
Step-by-step explanation:
The question pertains to a traffic rule on the safe distance required to make a u-turn. According to standard driving regulations, it is generally considered unsafe to make a u-turn when oncoming vehicles are closer than 200 feet. This distance provides the necessary time for the driver to complete the u-turn without causing interference to the flow of traffic and allows oncoming vehicles enough space to react and slow down if necessary. It is critical for drivers to evaluate the situation carefully and only perform a u-turn when they have sufficient visibility and space to execute the maneuver safely, without endangering themselves or other road users.