题一：
Not until he went through real hardship _____ the love we have for our families is important.
A. had he realized B. did he reali ze C. he realized D. he had realized
Not once ________ to Michael that he could one day become a top student in his class.
A. occurred it B. it did occur C. it occurr ed D. did it occur
题三：
“Never for a second ,” the boy says, “_ _____ that my father would come to my rescue.”
A. I doubted B. do I doubt C. I have doubted D. did I doubt
