Find a mistake in the four underlined parts of the sentence and correct it:
Among the students are many foreigners which attend Vietnamese language class 
at the center.
A. students
B. which
C. Vietnamese
D. at the center

Choose the best answer for the following sentence:
When I got home from classes, I found the door ___________. 
A. unlocked                
B. unlocking                
C.  to unlock                    
D. have unlocked

Choose the word that has the underlined part pronounced differently from the rest: 
however                   know                      follow                    show
A. however                   
B. know                      
C. follow                    
D. show

Choose the best answer for the following sentence:
Phong Nha _________ has been declared World Natural Culture Heritage. 
A. cave               
B.  rock                
C. cliff              
D.  pagoda

Choose the word that has the underlined part pronounced differently from the rest:
locate                      area                       state                    place
A. locate                      
B. area                       
C. state                   
D. place

Choose the best answer for the following sentence:
There are a lot of information _____________ the Internet, the matter is which onewould you choose to read and to believe.
A.  in               
B.  on                  
C.  above                 
D.  up

Choose the best answer for the following sentence:
___________ we change our farming methods if the government introduces new good ones? 
A. Will                  
B. Do                   
C. Shall                         
D. Have

Choose the best answer for the following sentence:
We have been studying together for ten years now. We are ___________.
A. workmate
B. pen pal
C. partner 
D. classmate

Choose the best answer for the following sentence:
Our country needs is a long-term policy for investment in science and ____________.
 
A. technique
B. technician
C. technology
D. technologist

Tìm khoảng nghịch biến của hàm số $\displaystyle y=2{{x}^{3}}-9{{x}^{2}}+12x+4$
A. $\displaystyle (1;2)$
B. $\displaystyle (-\infty ;1)$. 
C. $\displaystyle (2;3)$. 
D. $\displaystyle (2;+\infty )$.