Answer:
We check to verify that the step 
 is included in simplifying the expression.
Thus, option D is correct. 
Explanation:
Given the expression


 ← This is the step
Thus, the step 
 is included in simplifying the expression.
Thus, option D is correct. 
BONUS! 
LET US SOLVE THE REMAINING 
 


 


 

 

From the above calculations, we check to verify that the step 
 is included in simplifying the expression.
Thus, option D is correct.