Since this is homework, you need to show your best effort before anyone will provide any guidance. Members are expected to not simply provide answers for homework; you'll learn more if you have to work for answers.
Would your answer be the same if you knew that they wanted to use it to take a large family across the country on vacation or if they wanted to use it to haul a fifth-wheel trailer, or if they wanted to use it to go off-roading? There is seldom any meaningful answer to "best" unless there is some meaningful metric by which to evaluate whether choice A and better than choice B.
In this case, you have possible metrics such as power efficiency, single-point failure tolerance, uniformity, tenability, cost, and others. The answers are different depending on what the metric is.
One of these circuits will be considered really bad by most metrics, but there is at least one metric by which it would be considered best. Can you think of what that might be?
Since this is homework, look at each circuit and list as many pros and cons as you can think of.
You also need to know more about the LEDs. (I will not say which properties of the LEDs I am thinking about. If you don't know you will need to learn a bit more about LEDs.) There are some LEDs that would not work at all in one of the circuits.