Cho a, b>0 a+b <= 1. Tìm Min A= a^2 + (1/b^2)

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Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following question.

Never before ______ such a severe flood in this mountainous area.

A. do I see  

B. I have seen        

C. I had seen          

D. have I seen