--Im told that John had another car accident this morning.--I believe not. He so careless

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A. shouldn't have been
B. wouldn't have been
(答案→)C. couldn't have been
D. mustn't have been
解析：本题考查时态的掌握情况，问句是“有人告诉我约翰今天早晨出了交通事故”，答句应为“我不相信，他不可能这么不小心。”只有c项为此意思，shouldn't have done表示“本来不应该……”，mustn't have done表示“禁止做”。