Choose the best answer for the following sentence:
We must follow __________________________ .  
A. the will of the dead                
B.  the dead of the will 
C. the dead's will                   
D. the dead will

Choose the best answer for the following sentence:
Mammals have been in _____________ for many millions of years. 
A. existance                   
B. existing                        
C. existence                     
D. exist

Choose the best answer for the following sentence:
There is a pool of shoe styles available on the market. Which style you choose is just a matter of ___________. 
A. self preference                      
B. own preference                       
C. personal preference 
D. viewpoint preference

Choose the best answer for the following sentence:
“Diana is a wonderful ballet dancer.” “She ______________ since she was four.” 
A. has been dancing                
B. has been danced
C. is dancing                
D. was danced

Choose the best answer for the following sentence:
 The referee’s ______________is the most important in any sport competition.
 
A. decide                      
B. decisive                     
C. decision                 
D. decider

Choose the best answer for the following sentence:
I finally finished ___________________ at 7 p.m. and served dinner. 
A. cooking            
B. being cooked          
C.  to cook           
D. to be cooked

Choose the best answer for the following sentence:
It's much more convenient to take a _____________ and enjoy things that are carefully prepared for you.
A. package holiday                 
B. packaged holiday                     
C. packaging holiday
D. packed holiday

Choose the best answer for the following sentence:
Camping is hard if you're not used to ____________________ on the ground. 
A. be slept                
B. to be sleeping                 
C. sleep             
D. sleeping

Xét sơ đồ mạng điện ở hình vẽ có 6 công tắc khác nhau, trong đó mỗi công tắc có hai trạng thái đóng và mở. Số cách đóng - mở 6 công tắc để thông mạch từ P đến Q bằng:
A. 15.
B. 24.
C. 36.
D. Một kết quả khác.

Tìm số tự nhiên n thỏa mãn: $A_{n}^{2}=210$ 
A. 15
B. 12
C. 21
D. 18