[owlpower]

I understand that the vapour will consist of both cyclohexane and toulene, and it will cool, condense, and vapourise again in the process of fractional distillation. I believe the option should be A as the mixture is supposed to go up the column slowly.
However, a part of me also thinks it's option D, "nothing" because refluxing is supposed to happen. Am I getting the question right?

[Babcock_Hall]

I think that the question assumes that the highest point reached by the solvent is not changing over time.

[owlpower]

Thank you very much, that was very helpful. It is indeed option A.