Answer:
D 
Explanation:
Let's factor x2+8x+16 
x2+8x+16 
The middle number is 8 and the last number is 16. 
 
Factoring means we want something like 
(x+_)(x+_) 
Which numbers go in the blanks? 
 
We need two numbers that... 
Add together to get 8 
Multiply together to get 16 
Can you think of the two numbers? 
 
Try 4 and 4: 
4+4 = 8 
4*4 = 16 
 
Fill in the blanks in 
(x+_)(x+_) 
with 4 and 4 to get... 
(x+4)(x+4) 
 
Answer: 
(x+4)(x+4)