Choose the best answer for the following sentence:
We would like to thank the local enterprises we work _______________ to organize the event.
A. on cooperation with
B. on cooperation of
C. in cooperation with
D. in cooperation to

Choose the best answer for the following sentence:
If only I ___________ him now. 
A. see               
B. saw                   
C. have seen                
D. seen

Choose the best answer for the following sentence:
If something is on your __________, you are thinking or worrying about it a lot.
A. mind
B.  brain                    
C. head         
D. hand

Choose the best answer for the following sentence:
 No one seemed to notice my ____________ and I felt so lonely.
A. message
B. friendliness 
C. existence
D. living

Choose the best answer for the following sentence:
There are several ___________ to attract the attention of other people.
A. chooses
B. chose
C. chosen
D. choices

Choose the best answer for the following sentence:
Be quiet, please. We ______________ at the translation and you _________________ a lotof noise. 
A. are working - are making            
B. work - are making 
C. are working - make       
D. work - make

Choose the best answer for the following sentence:
I am reading this novel. By the time you come back from work I _____________________ .
A. shall finish         
B. will finish 
C. shall have finished                  
D. have finished

Choose the best answer for the following sentence:
She __________________ of great help to us since she ________________ for such a long timewith us.
A. has been - has lived         
B. has been - has been living
C.  has been - lived            
D. A and B are correct

Choose the best answer for the following sentence:
Books are a wonderful source _____________ knowledge and pleasure. 
A. with                       
B. of                     
C. in                     
D. about

Cho phương trình: $\displaystyle \left( {{m}^{2}}+2 \right){{\cos }^{2}}x-2m\sin 2x+1=0$. Để phương trình có nghiệm thì giá trị thích hợp của tham số là 
A. $\displaystyle -1\le m\le 1$ 
B. $\displaystyle -\frac{1}{2}\le m\le \frac{1}{2}$ 
C. $\displaystyle -\frac{1}{4}\le m\le \frac{1}{4}$ 
D. $\displaystyle |m|\ge 1$