選C
虛擬語氣：1.與事實(shí)相反的假設(shè)：
虛擬條件句：If +主語+動詞的過去式（be動詞用were）
主句：主語+should或would或could或might+動詞原形
例句：If I were you ,I should seize the chances to go abroad.
If I had time ,I would attend the meeting.
2.與過去事實(shí)相反的假設(shè)：
虛擬條件句：If +主語+had+過去分詞
主句：主語+should或would或could或might+have+過去分詞
例句：If you had taken my advice,you would not have failed in the exams.
3.與將來事實(shí)相反的假設(shè)：
虛擬與條件句：（1）If +主語+動詞過去式
（2) If +主語+were to+動詞原形
（3）If +主語+should+動詞原形
主句：should或would或could或might+動詞原形
例句：If you came tomorrow,we would have the meeting.