Answer:
B) 
Step-by-step explanation:
the equation is: 
we have an equation of the form

where

and we must complete the square to obtain a perfect square binomial,
we must add and substract the following:

which is:

and then the equation becomes:

where the terms
are the components of the perfect square binomial: 
and thus, the equation now is:

the answer is: B) 