I really think you are overthinking this.
First of all, we are asking a question that is explicitly stated in the video in this unit (the slide starting around the 9:40 mark).
In the Fundamentals course, there were several times you had to calculate voltage drop across loads in series, and the first thing you had to do was find the total resistance of those loads so that you could then calculate the circuit current. This question is meant to be a review of that.
Inherent in any multiple choice question is that you are supposed to pick the best answer of the choices given. In this particular question, we give you 3 possible answers: total circuit resistance, current, or voltage.
You would never calculate total circuit voltage – that is just a fact that will always be given to you.
And you can’t calculate the circuit current without knowing the specifications of the loads and totaling them up.
The information given about loads is usually their resistance.
Yes, sometimes wattage could be given, and if you had the expected watts for each load, then there is a way to use that to work your way through the calculations to eventually get voltage drop across each load. However, we didn’t show that or ask you to do that in the Fundamentals course or this one, nor did we give that as an option on this question.