Answer:
A. 

Explanation:
For this problem, we have to combine like terms. 
Let's look at the equation: 

 ,
, 
 ,
, 
 do not have any other like terms, so we keep all in the final answer.
 do not have any other like terms, so we keep all in the final answer. 
 and
 and 
 are like terms, so we combine them.
 are like terms, so we combine them. 

14 and 6 are like terms, so we combine them. 14+6 = 20
Let's put everything into the final equation: 

So, the final answer is A. 

Hope this helps! If you have any questions about my work, leave them in the comments below!