Of course Michael Frayn's Copenhagen is not about physics. It is about the memories and interactions of three important, passionate, figures struggling to make sense of a meeting that took place in Nazi-occupied Denmark in September of 1941. The question that dominates the play is why did Heisenberg, head of the German nuclear project, make that visit to Bohr, his old mentor, one of the creators of quantum theory and nuclear physics.

Since memory of the past is shaped by the present, and since each of the characters, particularly Heisenberg, has reasons of their own for wanting to reinterpret what their intentions were, we probably never can be sure what the actual reason for the visit was. (According to the quantum superposition principle, might it have been a combination of all of the various possibilities – all of the above, as the multiple-choice question puts it.)

But two of the three characters, Bohr and Heisenberg, happen to be among the founders of modern quantum theory – certainly one of the great intellectual achievements of the twentieth century.