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

John asked me_____that film the night before.

A. if had I seen

B. if I had seen

C. had I seen

D. that I saw

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

We_____touch since we______school three years ago.

A. lost / have left

B. have lost / left

C. have lost / leave

D. were losing / had left

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

It is said the Robinhood robbed rich and gave the money to______poor.

A. a/ a

B. a/ the

C. the/ the

D. the/ a

a, ta co : 10^n = 100...00( n cs 0)

 => 10^n -1 = 100...000 - 1= 999..99( n-1 cs 9)

 vì 9+9+..+9(n-1 cs 9) = 9. (n-1) => ĐPCM

b, ta co : 10^n= 100..00( n cs 0)

=> 10^n +8 = 100..00 + 8= 100..08( n-1 cs 0)

vì 1+0+0+...+0+8( n-1 cs 0)= 9 => ĐPCM