单选题 I ______ have written to him because he phoned me shortly afterwards.
  • [A] ought to
  • [B] must
  • [C] couldn't
  • [D] needn't


【正确答案】 D
【答案解析】[考点] 虚拟语气
[解析] Need not have done表示“其实本来不必……”，指过去已发生过的事，事实上没有必要。