Why are Clifford gates alone not enough for universal quantum computing?

Question: Why are Clifford gates alone not considered universal for quantum computation? A) Clifford circuits can be efficiently simulated classically under the stabilizer formalism, so non-Clifford resources are needed for universality B) Clifford gates cannot act on qubits C) Clifford gates always destroy entanglement D) Clifford gates cannot be represented by matrices Correct: A Explanation: Clifford gates are very important, especially in stabilizer circuits and error correction, but Clifford-only circuits are not enough for universal quantum computation. Non-Clifford gates such as T gates are needed. Topic: quantum computing / Clifford gates / universality