问题
选择题
about this computer program, a huge amount of time and energy .
A．Should I know; be saved
B．If I had known; can be saved
C．Had I known; would have been saved
D．Did I know; was saved
答案
答案：C
选C。考查倒装句和省略。含有should, had或were的虚拟条件句, 可省略if, 必须将should, had或were提到主语前。此处表示与过去事实相反的假设, 故选C。