Tính tổng $S$ tất cả các hệ số trong khai triển ${{\left( 3x-4 \right)}^{17}}.$ 
A. $S=1.$ 
B. $S=-1.$ 
C. $S=0.$ 
D. $S=8192.$

Cho tập A có n phần tử và k là một số nguyên dương với 1 ≤ k ≤ n. Số tổ hợp chập k của n phần tử của A là:
A. Pk.
B. .
C. .
D. .

Choose the best answer for the following sentence:
I don't think ______________ knows ____________ about it.
A. somebody - something
B. somebody - anything
C. anybody - something
D. anybody - anything

Choose the best answer for the following sentence:
The room ___________ once a day. 
A. should clean                      
B. should be cleaning
C. should be cleaned                      
D. should have cleaned

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