Multiple choice
Execute the circuit and measure. How likely is the outcome |11⟩?
const c = circuit(2); c.x(0); // X error on the control turns |00> into |10> c.cx(0, 1); // control is 1, so target flips: |10> -> |11> return c; // final state |11>: the X copied forward (weight-2 error)
Commit your prediction for P(|11⟩) — then run it.