Cho hình lập phương $ABCD.{A}'{B}'{C}'{D}'$ có cạnh bằng 1 (đvd). Khoảng cách giữa$A{A}'$ và $B{D}'$ bằng:
A.$\dfrac{3\sqrt{5}}{7}$  
B.$\dfrac{\sqrt{3}}{3}$                       
C.$\dfrac{\sqrt{2}}{2}$
D.$\dfrac{2\sqrt{2}}{5}$

Giá trị của $ x $ để biểu thức $ \dfrac{4\text{x}-5}{x-1}-\dfrac{x}{x-1} $ bằng $ 2 $ là
A.$ x=3 $.
B.$ x=4 $.
C.$ x=2 $.
D.$ x=5 $.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
The film…………(run) for ten minutes yet, but there's a commercial break already.
 
A.had been run
B.has not been running
C.hadn’t been ran
D.ran

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
We ... for the bus for 20 minutes now, I think the bus….......
A.have been waiting - has been crashing
B.have waited - has crashed
C.have waited - has been crashing
D.have been waiting - has crashed

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
The homework my teacher assigned me is endless. I ___________ it all day but still _______yet.
A.have doing/ have not been finishing
B.have done/ have not been finishing
C.have been done/ have not finished
D.have been doing/ have not finished

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
It’s time Tom had to tidy his garden. It’s getting ___________.
A.more and more messy
B.more messy and messy
C.more messier and messier
D.messier and messier

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Since he (leave) ______ here no one (see) ______ him.
A.has left – saw
B.had left – saw
C.left – have seen
D.left – has seen

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
He spent a year in India and loves spicy food. The _______ the food is, the _______ he likes it.
A.hot – more
B.hot – much
C.hotter – much
D.hotter – more

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Their new kitchen looks fantastic. They______it for 5 hours.
A.have redecorated
B.already redecorated
C.have been redecorating
D.didn’t redecorated

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Getting a job these years is becoming _______________ and the unemployment rate kept rising each year.
A.competitiver and competitiver
B.more and more competitive
C.more competitiver and competitiver
D.more competitive and competitive