What is the cost of probabilistic error cancellation?

Question: What is a major practical cost of Probabilistic Error Cancellation? A) It can require large sampling overhead because noisy operations are represented using quasi-probability decompositions B) It prevents expectation values from being estimated C) It only works on classical CPUs D) It removes the need for calibration data Correct: A Explanation: Probabilistic Error Cancellation tries to reconstruct ideal expectation values by statistically inverting noise. This can be powerful, but the required number of samples may grow significantly. Topic: quantum computing / error mitigation / PEC