What is the difference between:
Qu'est-ce qui marche le mieux ?
and the Que from the interrogative lesson Questions: Que ... = What?, e.g. :
Que marche le mieux?
What's the best way to recognize what is the best solution to use? The first thing that jumps out to me is that Que marche le mieux might be incorrect b/c there is not really a subject, but I would appreciate a more formal explanation, thank you!